Matters arising

April 2017

After the parking episode described recently, I think I have not written about my other parking issue, because parking is one of the least interesting and most discussed issues of modern times. Outside my garage there is a white line to indicate that parking is not permitted across the entrance. As we have seen when it was removed by the re-surfacing works this line served a useful purpose, but it was only just long enough, and cars parked legally would slightly obstruct the garage entrance, but not enough to stop me getting in and out. I wrote about this briefly in a previous post, and eventually did contact the council's white line department to ask if it could be lengthened, to which they said 'No'. However, after the re-surfacing work the line was re-painted at the longer length that I had been asking for. So that's interesting. Or, more accurately, it isn't. Enough with the parking already.

I went to a local meeting. Some money has been allocated to be spent on improvements to the park at the end of my road, and the council thought they'd ask the locals what they would like. There was already a prototype group to ask, because the Friends of the Park had been convened when the park was threatened with being taken over by cars, caravans and motor homes during the National Bowling championships in the summer. It was a good meeting, and surprisingly good humoured and constructive. The main problem seemed to be the newly installed skate park, which is very popular and attracting swarms of local 'yoof', but is also attracting their litter despite the many litter bins in the vicinity.

The yoof in attendance were polite and well-spoken and made good points. There were also representatives from the bowling club, the tennis club, local dog-walkers, parents and runners who are the main constituency of park users, as well as all the candidates for the local election taking place a couple of days later. It looks as though the most likely purchases may be outdoor gym equipment (but there is a separate pot of money that may fund this anyway) or a refurbishment of the under-used tennis/cricket pavilion to make it more usable for e.g. a cafe. My previous local councillor who I can no longer vote for was there, and I took the opportunity to thank him and express my regret that he would no longer be representing me.

Work news: I delivered the 'short carb counting course' pilot. Prizes are available for anyone who can come up with a better name - my best shot at the moment is Candi, which stands for Carbs and Insulin. This comprised four hours about carb counting extracted from our usual four days about Type 1 Diabetes, to deliver to people who can't spare four days and maybe don't have Type 1 Diabetes. We had five attendees and I think it went well. I have yet to look at the feedback sheets.

We also had a small meeting attended by our business manager, two doctors, three nurses and me. It was supposed to discuss the future of the insulin pump service, which is set to expand by about 10% every year. As usual the meeting was utterly pointless and did not result in any useful discussion or conclusions, but it was quite a nice social event within the department. We are having a follow-up meeting with just three of us, which may be more constructive. All I actually want from the meetings is to understand how our service is funded and managed. It doesn't seem much to ask, but so far I have failed to achieve even this small advance.

Two CPD courses for me last week as well - the first about Clinical Audit presented by one enthusiastic and knowledgeable man and one girl whose presentation style was simply to read out loud the text written on each Powerpoint slide. I tried to be constructive in my feedback, but she was terrible. I discovered quite a lot about Clinical Audit, including the fact that what I planned for evaluation of the short carb counting course isn't Clinical Audit at all, it's Service Evaluation. The other course was a compulsory three-year update on DESMOND, the Type 2 patient education product. Also very interesting, and delivered in the same rooms of the same hotel as the first big Techshare conference that I helped to launch and run in the 1990's.

Much leisure activity to report - the music group continues, with the prospect of me being the sole baritone saxophonist at the July concert because my fellow saxophonist has a previous engagement. There are significant exposed baritone solos in the pieces we are playing, and I am not at all confident of successful delivery, seeing as how I'm really not very good at playing the beast even though it is enormous fun.

I also spent a whole day with the Buddhists at our usual venue - a nearby village hall - and the weather was lovely and we did some meditation, some chanting, some discussion and another 'puja' ritual. I still don't think I'll be joining in with the rituals any time soon, but for the first time I really felt that I had made progress with the meditation. It's been so gradual that it's hard to detect, but it feels easier to do and in my everyday life I am employing some of the positive behaviours that it's supposed to promote, and and feeling better for it.

The LTRP took a step forward with the rebuild of the airing cupboard, which looks lovely and needs only to be painted. While they were here the carpenter and his mate were kind enough to carry my filing cabinet upstairs to the new office, about which I am disproportionately excited. I also went back for a second meeting with the woman from the alternative kitchen supplier who has very strong views on her products and doesn't mind sharing them, and who speaks very loudly. I am trying not to be too influenced by these factors and to focus on the content rather than the style of delivery.

Bolus advisor masterclass part 2: Post-prandial correction

Cotswold Falconry Centre, April 2017

The first instalment of feedback from the recent course I attended was mostly about adjusting insulin dosage to account for fat and protein content of meals. The second half of the course left several delegates behind...

Post-prandial correction doses

This was by far the nerdiest section of the course, and took quite a bit of concentration and asking the presenters to 'just say that again more slowly.' It was all about how the bolus advisor technology built into blood glucose meters and insulin pump handsets works out correction doses of insulin when blood glucose is high following a meal.

Unless you have a fully functional pancreas, you cannot avoid your blood glucose rising after a meal, even if you have injected the 'right' amount of rapid-acting insulin. Trials have shown that for the rapid insulins currently on the market, the ideal time to inject is 15-20 minutes before a meal. This is usually impractical, because you don't know how much insulin you will need until the food is in front of you, and then you don't want to wait 15-20 minutes before eating it. So the period when the injected insulin is reaching the peak of its action ('offset time') lags behind peak glucose entering the bloodstream, and this is one reason why post-prandial blood glucose tends to rise more than for a person without diabetes ('meal rise'). But if you've worked out the right amount of insulin, your blood glucose should return to 'normal' levels within four hours, which is the 'acting time' for rapid insulin.

So if you monitor your blood glucose less than four hours after your last bolus or injection, the blood glucose level that you see may actually decrease further without any action from you, due to 'insulin on board' - active insulin still in your system. So how do you know whether to correct it or not? At any time within four hours of your last injection, how high is 'too high'?

Imagine a scenario where your blood glucose level is within the ideal range before a meal, you have counted 60g carb in your meal and your insulin to carb ratio is 1 unit for every 10g - this means you will need 6 units of insulin. Roche told us that other manufacturers' algorithms assume that all insulin injected is 'active' insulin. So if your correction ratio is 1 unit of insulin to reduce your blood glucose by 3 mmol/L, then immediately after the meal your blood glucose could be up to 18 mmol/L higher than its pre-meal level and you would not be advised to take a correction dose because of the 6 units of active insulin. Roche also told us that other manufacturers assume a linear reduction in blood glucose, so after 2 hours your blood glucose could still be up to 9 mmol/L higher than the pre-meal level and no correction would be advised.

Fig 1. Correction is not advised if blood glucose falls below the line

This is not good. Even in the worst case scenario, blood glucose should not rise this high after a meal. There's no perfect number to aim for, but (assuming the meal wasn't Frosties) I would be happier with a meal rise of no more than 4 mmol/L, and 3 mmol/L would be even better.

Roche's algorithm makes quite a different set of assumptions, the main one being that only pre-prandial correction doses (insulin injected because pre-prandial blood glucose is too high) count as active insulin after the meal. Insulin injected for carbs is accounted for, and is not available to act on a high post-prandial blood glucose level. They say they have evidence to support this assertion.

So for Roche, a correction is required if the blood glucose rises higher than the 'meal rise' setting during the 'offset time'. After that a linear decrease to the pre-prandial level by the end of the 'acting time' is assumed. If meal rise is set to 4 mmol/L, offset time is 1 hour and acting time is 4 hours, then a blood glucose rise of 9 mmol/L at 2 hours would definitely suggest a correction. The shorter the offset time and the smaller the meal rise settings in the handset, the more aggressive the correction regime. For someone frail and elderly or prone to hypos it makes sense to have a higher meal rise and a longer offset time, to minimise risk of over-correction and hypoglycaemia.

Fig 2. Correction is indicated for the same post-prandial blood glucose level as Fig 1

Blood glucose correction after snacks

This was the hardest part of the course to understand, and therefore to explain. It would be so much simpler if people with Type 1 diabetes didn't eat between meals! But given that they do, they need advice on whether to correct blood glucose after a snack. The aim of the 'snack size' setting is to determine whether to apply a 'meal rise' and 'offset time' or not.

The 'meal rise' setting doesn't change depending on the size of the meal; it is the same whether the meal is small or large. So the 'snack size' setting is the carb threshold between applying a meal rise or not. If 'snack size' is set to 20g of carb, then for snacks up to this amount correction will be indicated afterwards if blood glucose is above the line in the previous graph. If a 'snack' 2 hours after a meal contains 30g of carb then the meal rise is applied at that point and a new graph is drawn, with corrections only advised for blood glucose levels above the new line.

Fig 3. Presence of the meal rise allows post-prandial blood glucose to be higher without advising correction

This is pretty sophisticated stuff, and I'm pretty sure that none of our patients understand how these settings are used. I'm only just working it out as I write this. What it boils down to is that most people using a basic type of meter have to take a stab in the dark when correcting post-prandial blood glucose levels, but people who are using this technology should get a good indication of whether to correct and how much insulin to give, as long as the settings have been adjusted to meet their particular requirements.

I always try hard to make sure that the main insulin to carb ratio and correction factors are right, but I have been less attentive in the past about the meal rise and snack size, because up to now I didn't understand what they were for.

The last point to mention is what we can do for people using pumps and meters that use the linear algorithm in Figure 1, which don't give useful advice about post-prandial correction. The team delivering the training suggested shortening the acting time setting to 3 hours instead of 4, because then at least a few more high blood glucose levels will fall above the line. This is not ideal, but the best they could come up with.

Bolus advisor masterclass part 1: Counting fat and protein

Seville, November 2016

It's been a few weeks since I attended this course, and it's time to assemble my thoughts and learning points. It was a terrific day and I certainly learned quite a lot, most of it very relevant to my work with people with Type 1 diabetes. In fact, two days after the course I was passing on some of the information to the group I was teaching at the time.

It is important to note that the day was hosted by one particular pump manufacturer, Roche, so there is a likelihood of bias. Having said that, I think the majority of information supplied was correct - it would be fairly straightforward to check, although I haven't done so. The first topic covered in the day was a comparison between the specifications and capabilities of the different insulin pumps on the market. Then we focussed on the algorithm that each manufacturer uses to guide the user in the amount of insulin to give in various circumstances: for exercise, for high fat and protein meals, and to correct high blood glucose levels after a meal or snack.

Exercise

The guidance around exercise wasn't very different from what we already advise - if you're exercising within 90-120 minutes after a meal you could give less insulin for the meal; if not then you'll probably have to eat or drink some carbohydrate to prevent blood glucose dropping, and if you're using an insulin pump you've also got the option of reducing background (basal) insulin. I've written extensively and comprehensively on the knotty topic of exercise and Type 1 diabetes. It's a challenging area, and management.is very individual. All the pumps work in a similar way, although the Roche handset has some features that help with the mathematics of percentage reductions.

High fat and protein meals

OK, this is going to start getting technical (although nowhere near as nerdy as the section on post-prandial correction doses in part 2).

For people with Type 1 diabetes, the evidence suggests that best management of blood glucose levels, and therefore long-term health and freedom from diabetes-related complications, comes from matching insulin injected and carbohydrates consumed. (Just for contrast, the approach for people with Type 2 diabetes in the first instance is weight loss).

The first point that hit home during the course was that although we focus on counting the carbohydrate in a meal, there is a contribution to blood glucose that comes from the protein and the fat in a meal. When we focus on carb counting, there is an unspoken (and for me until now, unrecognised) assumption that the meal is constituted of a 'normal' proportion of carbs, fat and protein. I actually know this to be true, because we have found when someone with Type 1 goes on a very low carb diet they need more rapid insulin with meals than the carbohydrate content would suggest.

Fat and protein have another effect alongside their contribution to blood glucose levels - they also slow down the digestion of carbohydrates. The action profile of insulin can't be adjusted to suit the meal composition - rapid insulin has a fixed onset, peak and acting time that doesn't change, so giving insulin in the standard way before a meal when it's a high fat/protein meal doesn't work very well, and post-prandial blood glucose often ends up way higher than one would like.

Up to now, conventional wisdom suggested that for a high fat meal carbs should be counted as usual, but the matching insulin dose should be delayed and/or split (if on injections) or spread over a longer time period (if on a pump), to account for the delay in digestion and later peak in post-prandial blood glucose. This course not only suggested that more insulin is needed because of the greater contribution of fat and protein to blood glucose, but gave some useful guidelines on how much more is needed, and how it should be delivered.

Six different high fat/protein meals were listed: fish and chips, Indian and Chinese takeaway, pizza, pasta with creamy sauce and fast food (McDonalds, KFC etc).  The following procedure was recommended separately for each.

As a first attempt, you should give 25% more insulin than you need for the carbs and deliver 50% at the start of the meal, and 50% an hour later (if on injections) or over 2.5 hours (if on a pump). Then, to see if these percentages are right, you should monitor blood glucose at 2.5 hours and 6 hours without having any more food or insulin. This will work best if your blood glucose level is within the normal range before the meal.

The 2.5 hour test is to find out whether the 50/50 percentage split is right. If blood glucose at this stage is more than 4 mmol/L higher than it was before the meal, then more insulin is needed up front - they suggest increasing by 20% at a time (i.e. switching to a 70/30 split next time). Conversely, if blood glucose is lower at this point than before the meal, the split should be changed to 30/70.

The 6 hour test is to find out whether the 25% extra insulin is right. If blood glucose at this stage is between 2 and 6 mmol/L higher than before the meal, next time add on another 10% - instead of 25% extra, add 35%. If at 6 hours blood glucose is more than 6 mmol/L higher than before the meal, next time add on 20% (to 45% extra). Conversely, if blood glucose is lower at this point, then next time knock the percentage down by 10% to 15% extra.

Multiple experiments may be needed to get the best results! Apparently parents are often taken aback when their Type 1 children come home from a carb counting course and assert that they've been given homework that requires them to eat fish and chips, takeaways and fast food.

Coming soon: Part 2 will contain even more technical stuff about how to manage post-prandial correction of high blood glucose levels.

Seize the moment to blog

Garden rose, June 2015

It's no use trying to compose careful prose and produce a well-crafted blog post about some aspect of my work or leisure that has made me think of something clever or interesting. There's no time. I have a mountain of paperwork, a backlog from my holiday - I knew there was a reason that I only go away for a week at a time. Then I was away for another two days on a course (that I want to write about) and then my week was stupidly busy and I was away for another weekend. So I'll just bang out some words about anything that occurs to me and have done with it.

We have a problem with our plumbing at Lola Towers. Mr A told me last week that the hot water had stopped running, but then it started again. We put it down to polystyrene balls - a very long time ago, one set of incompetent plumbers allowed polystyrene balls to get into the water system. On reflection, we haven't had any trouble for quite a while, so when the hot water failed again when I got back from my weekend away, I sought the advice of a friend who had that very weekend suffered something similar. Following his advice we ventured up into the loft, where the header tank for the hot water turned out to be empty. That was Sunday night, and I wasn't about to call for an emergency plumber seeing as the cold water was running fine and it was an intermittent fault - by Monday morning the tank had filled again.

I am an organised person, and I have many lists that remind me of things that need to be done. I find it impossible, however, to manage to simultaneously do the things on the list that I find difficult; I can just about manage them one at a time - partly because of the difficulty, but also because I have very little time to myself at work due to multiple patients and full clinics and delivering training off-site, and because there is no mobile phone signal in my office. To make a mobile phone call I have to leave the building and stand outside the door, and then it's difficult to write things down, and I can't refer to my online diary because the computer's inside, and if there's no answer I can't leave my number for them to call back because there's no signal when I go back into my office...

So I try to achieve one difficult task a day, and there are many tasks waiting. On Monday it was a call to a solicitor, and today I managed to call the plumber. (There is also the problem of when to arrange for him to visit, as Mr A and I are both working full time at the moment). Tomorrow I need to call the accommodation we have booked for New Year, on Thursday I need to send a letter of mild complaint to the accommodation I stayed in on Saturday night (Lola II is helping to draft it), and you would not believe how dirty the shower is. And there's that huge pile of paperwork that needs sorting out or else my car will not have a parking permit in August, among other slightly less urgent issues.

Then on Thursday there's the second week of our current carb counting course, so I have to cook some carbs for them to count. That means baking a potato and cooking measured amounts of pasta and rice on Wednesday evening to take to work on Thursday. This is a) to demonstrate the change in weight of raw vs cooked food (rice and pasta increase in weight, baked potato decreases in weight but carbs are unchanged for both) and b) to encourage the participants to weigh/measure these hard-to-estimate starchy carbohydrate foods, so that they will know for example how many carbs are in a standard tray of takeaway rice.

And of course I want to keep up the running, and my elbow is pretty much better so I'd like to go back to badminton, and there's the clarinet choir which is staging a concert in a couple of weeks. And I need to buy a new car, and new trainers, and waste paper baskets, and a bedside lamp, and put the charcoal picture that I drew at Mr M's birthday event into a frame, and re-pot and rejuvenate my house plants, and now the 15-foot rose bush and the enormous wisteria need pruning. I've used weedkiller on the patio weeds, but they need to be cleared, and all the rubbish littering the garden taken to the dump. My email inbox is bulging with messages that aren't important enough to be dealt with straight away but not unimportant enough to be deleted, and I am well behind on reading my blog subscriptions.

At work I have a similar number of issues. I was determined with this change of career that I would try and avoid the frustration of being unable to change the world by keeping my head down and letting the world sort itself out. It turns out that I can't seem to do that. Before I went away to America, I wrote a very apologetic note to my manager, detailing three pages of projects that I have taken on but are being thwarted by various barriers: procedural, technical and human.

I want to have a Internet-enabled data projector in our education room. I want to create a website to support our very low carb lifestyle group. I want to be able to show web content to our patients that is blocked by the Trust, including social media and videos. I want to support a new 'transition' clinic for young people moving from the paediatric to the adult diabetes service. I want to be able to offer patients the option of very low calorie 'diabetes reversal' diets that include meal replacement products. All of these need someone else to do something or agree to something, but instead of getting these things that I want, I have been asked to cover an extra clinic in the community on a Tuesday afternoon, and - the horror! - three half-days of ante-natal clinic over the summer (one of my colleagues has left and there is a gap before her replacement starts). And I have stupidly followed up a very good idea from one of my colleagues which needs me to do even more organising and coordinating.

I appreciate that these are problems that some people would be happy to have in place of the real and serious problems that they are having to deal with, but we all would like an easy life, wouldn't we?

Diabetes services

Greek sunset, June 2014

I've got a half-written blog post that I've been trying to finish, but it's taking ages because it needs a bit of thinking time and I'm just not getting round to it. So I'll do some writing off the top of my head, just to keep things ticking over.

I'm still working five days a week, being paid for about five hours on that fifth day doing general dietetics on the wards, which means mostly nutrition support. The hospital is a small one with only six wards, and holds patients who are not acutely ill and/or who live in the area. They are generally old and not actually needing further treatment but cannot go home until some sort of provision is arranged to make sure they can cope (a 'Package of Care'). Nearly all those who need dietetic input are not eating or drinking well, usually because they have dementia. I absolutely hate it. I have two weeks to go before the Dietitian who has been off sick is due to return, and I shall do everything in my power after that to be completely unavailable for this type of work in future, although there will be a lot of moral pressure to 'help out' if a similar situation happens again.

My real job is still very interesting. I have managed to start two people on the very low carb plan, but unfortunately one did not return for the follow up appointment and wasn't answering the phone when I rang. My first Structured Education course for people with Type 1 Diabetes finished this week. This is designed to give people a lot of information and practical experience of how to best manage their diabetes, and we run it one day a week for four weeks. We had eight attendees, and all of them seemed to get a lot out of it. I found it a little stressful to have so much responsibility for delivering material that is so critical to the course.

At least half of the course is about carbohydrate counting. This is a skill that is fundamental to good control of Type 1 Diabetes for those who want to have the flexibility of eating what they like when they want to. Teaching carb counting is a core skill for a Diabetes Specialist Dietitian, and I would say I have reached an intermediate skill level - not too bad, but I've only been doing it in earnest for a few years. Nearly all of the people on the course have had diabetes for much longer than that.

Despite my nervousness, it went quite well, although I think I can improve with practice. We cover all sorts of ways of estimating the carbohydrate content of food - using food labels, weighing food and using reference tables, using apps, websites and pictures, and plain and simple educated guesswork. The part that makes me a little bit uncomfortable is that while my estimates are based on my experience with a number of different people as a day job, I don't actually act on the data and inject insulin, so I don't get any personal feedback about the accuracy of my estimates. When I get it wrong, it's someone else that suffers. I take this responsibility very seriously, so I often lose sleep worrying about whether someone I've seen in the day is going to end up with very high or very low blood glucose as a result of something I've said.

As well as the course and the individual consultations, there has been some discussion in the Trust and the Clinical Commissioning Group about funding to expand the very low carb programme that we offer. This has caused some controversy, because we haven't any solid evidence for its value in our service. We have lots of anecdotal evidence of patients who have found it life-changing (in a positive way), and we have a spreadsheet with lots of data, but the data hasn't been analysed and there's been no data collection from those who haven't found it helpful, nor have we sought views from anyone who may have experienced negative effects.

There are a number of healthcare professionals in our Diabetes service who are positively messianic about the plan, and they are all in favour of the expansion in funding because they have seen so many people find it beneficial. Having joined the service so recently I am more sceptical, and feel that we must carry out some analysis of our data to provide evidence of benefit and investigate any negative aspects properly. Our Team Leader has very sensibly defused the situation with an eminently rational proposal, including the view that we should be offering people choices rather than putting all our energies into selling the low carb idea.

Whenever I have met up with other Diabetes Dietitians, I have asked them their views on very low carb diets. So far I haven't met any that are offering anything like our plan, but they have all been very interested in hearing about what we do. I would like our next stage to be a proper audit of what we have, if not a research project culminating in a peer-reviewed publication, but I'm not volunteering for the job.

Week two

'My' office

The first day of my second week saw me thrown in well and truly at the deep end. I arrived bright and early, hoping to find time at last to get the room sorted, discover the contents of the filing cabinet, and look for all the official diet sheets or patient information or whatever I could find. Instead, I found a) a note from the main DSN saying she forgot to mention she and the other principal DSN wouldn't be around until lunchtime, b) a list of 23 patients who were due to be seen by the doctor that morning, of whom I could see as many or as few as I chose. I also found a small table had appeared in 'my' room, which was absolutely ideal for sitting with patients.

That was a difficult morning, because I didn't understand what was going on or what was expected of me. I tried to get an explanation from the Support Worker and the DSN working in the clinic, and they did tell me how the doctor worked and what all their roles were, but despite repeatedly asking for suggestions, I didn't get much help with what I was supposed to do. I did the best I could, and at the end I discussed how I'd found it a bit hard going, at which point the DSN said "Well, Dietitian X [one of my colleagues who comes over to participate in a joint renal and diabetes clinic] does it like [this], and it seems to work very well." That's what I wanted to know at the start of the day; I don't know why she didn't tell me then. It's all a very big learning curve.

Then on Wednesday I went to the meeting with four other Dietitians, three working in Diabetes in the big hospital and the community, and one working with obese patients. There are distinct differences in the services offered by this team compared with my previous team - for example, I used to offer support for a Very Low Calorie Diet (using meal replacements like SlimFast) to enable weight loss; this team advocates carbohydrate reduction and has two different programs to support this approach. My carbohydrate reference tables went down very well, but my hypo treatment illustrations provoked some discussion about whether the appropriate treatment should be 10g or 15g fast-acting carbohydrate followed by 15g or 20g slower acting carbohydrate.

The main problem through the meeting was that I had to interrupt them repeatedly to get them to explain all sorts of jargon and references to people, events, places, teams, programs and treatments that I wasn't familiar with. I didn't manage to get the full overview of the service that I was hoping for, but I can easily get back in touch to clarify and get more information at a later date.

I still haven't had time in 'my' office to get the hang of what goes on. I was looking forward to time on Thursday, when it didn't seem that there was anything scheduled. At the end of Wednesday, however, the DSNs mentioned that they wouldn't be around on Thursday because they were attending a study day on Type 2 Diabetes, so of course I asked if it would be suitable for me to attend, which it was. So that was where I went on Thursday.

It was a full day of talks from various doctors, nurses and researcher, but Ben Goldacre's views were thoroughly borne out when it became clear that the sponsor's products were featured heavily. It was useful to me anyway, because my knowledge of Type 2 and its features and treatments is a bit flaky. One of the strongest non-pharmaceutical messages that was delivered was that if you are diagnosed with diabetes and continue to smoke, then your risk of death is so enormously raised that if you understood the probabilities you would be thoroughly shocked. Maybe even shocked enough to stop smoking. I don't remember the numbers, but maybe I'll look them up when I get a spare minute. I have no idea when I will ever get a spare minute again.

I saw patients on Friday, which is my 'short' day, so I was home early. I had foolishly suggested to Mr A that we might go out on Friday night to a gig in which a friend was playing, and he was quite keen. I, however, had come to regret the suggestion and would have paid a considerable sum including body parts to be allowed to stay at home on the sofa. We went out, it was good, we came home very late indeed, and I slowly recovered over the course of the weekend. Then the working week started again...

Gastroparesis (part 2)

Groombridge Place, June 2013

In part 1, I described the symptoms of gastroparesis, what might be causing it in someone with diabetes, and the problems that arise - gastrointestinal symptoms, poor glycaemic control, malnutrition and weight loss, and depression. Now I'm going to write about possible treatments.

Nerve damage, if that's what is causing the problem, is irreversible. We can't (yet) mend nerves: once they're gone, they're gone. There doesn't seem to be an option to fix the faulty pacemaker cells either. But it is always useful to run through a list of things that will definitely not be helping. For example, opiate drugs are known for their constipating effects, and should be replaced with alternative painkillers if pain relief is necessary. Cigarette smoking has been shown to delay the gastric emptying of solids. Unfortunately, high blood sugar has also been shown to significantly delay gastric emptying, which is of no comfort to the person with diabetes who has been trying unsuccessfully to manage wild swings in blood sugar in the face of unyielding opposition from the gastroparesis itself. So I wouldn't bother opening that particular can of worms.

There are three methods used to help improve gastric emptying: pharmacotherapy (i.e. drugs), diet and surgical approaches. Two types of drugs can help with symptoms: prokinetics, which help to speed the intestinal contents on their way, and anti-emetics, which are used to prevent nausea and vomiting. These are routinely used, but changes to diet can be more effective than the medicines.

The Glycaemic Index (GI) is often used to assist with blood glucose control and weight management, and describes the speed at which carbohydrates are digested. High GI foods e.g. foods containing large proportions of monosaccharides and disaccharides (sugars) are digested quickly, and their glucose payload can reach the bloodstream before subcutaneous insulin has had time to get there, causing blood glucose to rise beyond the desired range. Low GI foods (complex starchy carbohydrates) such as oats and pulses are digested more slowly, and therefore deliver glucose to the blood slowly and more controllably, and keep you feeling fuller for longer. Unlike the majority of people with diabetes, high GI foods may help someone with diagnosed gastroparesis. These foods tend to contain simple sugars or processed carbohydrate and little fat and fibre - sweets, white bread, mashed potato.

Another good reason to avoid fibre, apart from its role in slowing gastric emptying, is that as it hangs around in the stomach it can contribute to the formation of unwanted fibrous masses called bezoars. The disadvantage of avoiding fat, however, is that someone with chronic gastroparesis is at risk of malnutrition, and could do with the calories supplied by energy-dense fatty food.

The diabetologist who referred the patient with gastroparesis to me suggested that a low carbohydrate diet might help reduce the volatility in blood glucose levels. The problem with this approach is that taking out the carbs leaves an energy deficit that can either be filled by protein or fat. Protein increases feelings of satiety, which is certainly not what we want, and fat slows gastric emptying. Blood glucose levels may be better managed with a greater proportion of high GI carbohydrate, which might actually be released from the stomach in a more predictable manner.

Research suggests other dietary recommendations, both to relieve symptoms and to maintain nutritional status. Small frequent meals are digested better than three large meals a day, and 'particle size' makes a difference - food should be chewed well, and liquids seem to leave the stomach more easily than solids. A patient might be prescribed three liquid supplements a day, adding a much needed 900 calories. Positioning during a meal, and sitting up and/or walking post-meal can promote gastric emptying; alcohol and carbonated drinks tend to exacerbate symptoms of bloating.

Placing a feeding tube below the stomach and pylorus in the jejunum (upper small intestine) allows nutrition to bypass the problem area, but brings with it the risk of infections and the inconvenience of having to be hooked up to a feed pump for hours at a time - jejunal feeding has to be much slower than feeding into the stomach. If nutritional status continues to decline, intravenous (parenteral) feeding is a possibility, but brings a whole new range of potential complications.

As well as addressing symptoms and nutrition, there are those pesky blood sugars to consider as well. Eating a meal containing carbohydrate requires a matching dose of insulin in order to maintain blood glucose within the desirable range, but we have seen that giving the insulin at the usual time (before, during or immediately after the meal) doesn't work if the glucose hits the bloodstream over a period greater than the lifetime of the insulin. So we could try splitting the insulin dose, perhaps giving 30% of the total dose just after eating, and the remaining 70% after an hour, or two, or whenever we think blood glucose is rising.

If you don't want to end up as a pincushion, this type of insulin regimen can be managed much more comfortably and conveniently with an insulin pump, which can be programmed to deliver insulin at whatever rate you desire. Delivering 6 units of insulin at one-tenth of a unit every five minutes over five hours can't be done with conventional insulin injection devices, but is a piece of cake with a pump.

Unfortunately the NHS doesn't fund Continuous Glucose Monitoring (CGM) systems, which have a subcutaneous sensor that samples interstitial fluid every five minutes linked to a device that translates the reading into an estimated blood glucose level. We lend these systems to patients to wear for just seven days at a time when we can't work out what their blood glucose is doing. Otherwise, users have to buy the kit and consumables themselves, which works out rather expensive. Although not mentioned in the research papers I have read about this condition, I think that CGM in combination with an insulin pump would be a valuable and effective approach to managing blood glucose with gastroparesis.

Finally, there are more technical and innovative options to try.

• Gastric electrical stimulation (GES) was approved in 2000 in the USA. Similar to a heart pacemaker, the GES device is implanted next to the stomach and mimics the role of the gastric pacemaker cells, stimulating and enhancing vagal function and muscle tone. 
• Botox (Clostridium botulinum toxin) is a muscle relaxant used cosmetically to reduce facial wrinkles, but will relax muscles elsewhere to therapeutic effect. Injecting Botox into the pyloric sphincter may cause it to relax sufficiently to allow better gastric emptying, but trials have shown this effect to be short-lived. 
• In future, that universally-cited panacea 'stem cell therapy' may be relevant, providing a way to replace or rejuvenate those faulty pacemaker cells of Cajal.

Mr M and his insulin pumps

mylife OmniPod insulin pump wireless controller and Animas insulin pump with tubing

I mentioned a while ago that I had commissioned a guest post from Mr M, who has a new insulin pump. He has come up with the goods - a blog post comparing and contrasting his old and his new pumps, as well as providing some insight into the world of insulin pumping.

Hello ... Mr M here with my first contribution to the wonderful world of Lola Life.

Regular readers may already know that I have Type 1 diabetes and use an insulin pump. As I have changed insulin pumps recently Lola I asked me to write something about the two pumps.

My old pump (affectionately named Stanley by the lovely Lola II) was an Animas 20 20 pump which clipped on my belt [pictured at the top of the post on the right] and had tubing leading through my clothing to a patch [containing the cannula that delivers the insulin] on my waist or leg. I have had Stan for four years, and has had to been sent back to his parents three times – once because of the buttons sticking, and twice through water leakage.

Stan has been upgraded to Whitney (aka New Stan) who is a mylife OmniPod. Whitney came in a huge box and I wondered if I had been given a toaster. But no, it was my new pump.

New OmniPod pump patch

The new pump has two parts: the pump control unit, which is about the size of a smart phone – though four times as thick [pictured at the top of the post on the left] – plus a matchbox size patch which sticks to my leg, arm or stomach and contains the pumping mechanism and insulin [and the cannula that delivers the insulin]. The two are linked through a wifi system.

Stanley swinging back and forth

Now I had become quite attached to the old pump and not just literally. The most annoying feature though was that the small patch - about the size of a 2 pence piece – often came unattached, either because it didn’t stick down properly, or, more often, because the cord got caught when taking my trousers off. This happened frequently enough for me to have two patches attached at all times so I could switch to the emergency one if the first came off.

Old Animas pump patch

So… when I was offered an upgrade at the end of my four years, I decided to go for the wireless option (or rather, the tube-less option).

New Stan has the obvious advantage that being a wifi option, the tube tangle problem doesn’t come into play. After a month or using it, none of the patches have even come near to falling off. This may be because there is a large sticking area, or because the pump tells you every three days to change it, even if there are a few days of insulin left. (Stan used to just tell you when the insulin was going to run out). This does feel like the manufacturers trying to get you to use more patches than you need to.

Apart from the obvious wifi (or tufi?) advantage, pluses of the OmniPod over the Animas is that the basal programmes can be copied into a new programme so you can tweak it. For those who haven’t had advice or training in diabetes, a basal programme is the schedule of how much background insulin to give at which times, and on the Animas, you had to write all the times and figures down, then re-enter them into a new schedule which could take 20 minutes to do, with the potential of entering something incorrectly.

Another big advantage is that it is combined with a blood glucose meter – and as you get the pump control unit out each time you eat, there is more tendency to also test your blood than you would if you had to find your blood meter. There are also some fancy graphs on it so you can see your blood sugar results, and useful carb intake lists etc. There is also the advantage that my hospital can download my results – though this does of course assume you want them to know the actual results!

However, it is not all positives. There are some possible serious quirks. One is that if you are about to eat, and test your blood sugar – if it comes out low, the pump won’t calculate how much insulin you need for your carbohydrate intake – so you have to either guess, or remember to take some insulin 5 minutes later when the test result has cleared.

[Ed's note: 'guessing' is how people with diabetes who don't have a 'bolus advisor' estimate how much insulin they should take!]

The Omni Pod also doesn’t tell you how it calculates the insulin it suggests you need, but just the end figure. This is different from the Animas which would tell you that you needed X for the carbohydrates, and that it was taking off/adding Y for the blood sugar adjustment, and then would take off what insulin it had given you recently (as this will take some time to act). The reason this is useful is if you have just started a meal and given yourself insulin, then test yourself and find you are high, both pumps think “I have just given you insulin” so suggest you don’t have any more – however, if the food hasn’t actually been eaten yet, you may want to ignore the deduction for “insulin just given” as you want to have some more for the high blood sugar, and the insulin can deal with the food which is about to be eaten. 

On a lighter side (or maybe darker), the screen time out is only a maximum of 60 seconds and so it is impossible to change the pump patch without it timing out a few times – not a major issue but annoying especially as it would be an easy thing for the manufacturers to fix.

Finally, there is a negative side to the wifi facility. One of the selling points of wifi is that you don’t have to carry it around – but the same logic also means that as it isn’t attached to you, you can leave it behind without realising it. This doesn’t cause any changes to the background delivered, but means you can’t eat any carbs. I asked the rep about clips and bags to carry the unit (the Animas had a clip which made it look like a pager); the rep said it didn’t need to be carried so they didn’t do one. This sounded like an oversight and given the size and weight – is a problem for men in the summer as we don’t tend to have coats or handbags to carry things in.

In short, I think the wifi device is a better option, but Omni Pod could make a few software changes to improve it, and provide a clip or bag to attach it to your belt. However, the Animas device has a better designed piece of software and also makes you look important as you have a pager, while the Omni Pod makes it look like you are always on your mobile texting!

Thank you, Mr M! And a small prize* to anyone who can come up with the explanation of the new pump's name. All the clues are there for you in the text!

* not really

Back to school

Deutches Museum, Munich, March 2013

I spent two days last week at university: "Learning Beyond Registration - Diabetes 1". The registration that I'm learning beyond is that issued by the Health and Care Professions Council, which is the regulatory body for the Dietetics profession. The module can stand alone, or can form part of a Masters qualification.

Teaching is done at the university where I studied for my Dietetics degree, and the campus has changed surprisingly in two years. There is a big hole where one building used to be, there is a whole new building where there used to be an open space, there is a brand new cafe and shop, and various other upgrades to facilities, including pay and display parking which used to be free. It was also quite sunny and the cherry blossom was in full bloom, showing off the beauty of the countryside campus to full effect.

There are five of us taking this module, where in previous years there have been many more (I think a previous class of more than thirty was mentioned). Five was a good number, and three of the others had less experience than I do; we all had lots of opportunities to ask questions. In fact, day 2 was spent with an experienced diabetes Dietitian doing nothing but asking question after question.

Day 1 was more structured. The morning covered the evidence base, including a very useful document that summarises all the evidence behind the nutritional guidance that is applicable to diabetes. In the afternoon we went over the evidence of increased cardiovascular risks associated with both Type 1 and Type 2 diabetes with a very knowledgeable Dietitian from London, as well as looking at the different medications available and some of their side effects. We ran out of time at the end and skipped through insulin pumps, which was fine because I know quite a lot about pumps.

Day 2 was my perfect day. From 9 am until 4 pm we talked about anything and everything about diabetes - insulin, weight management, carbohydrate counting, glycaemic index, alcohol, physical activity, renal function and lots more. The role of the multi-disciplinary team, prescribing, low calorie and very low calorie diets, low carb vs low fat diets, the latest 5:2 'Fast' diet, glucose metabolism and competitive sport, glycaemic rebound following a hypo, the dawn phenomenon, glycaemic profile after alcohol or activity, matching insulin profiles against individual requirements, the use of 'old' vs 'new' insulins and their cost, the comparative cost of other medications, working with difficult patients (and colleagues), gestational diabetes, enteral and parenteral feeds with insulin, educational resources, new technologies like Skype clinics, different blood glucose meters, issues to consider on holiday (especially an activity holiday), and there was probably more.

After some careful discussion, I think I have got to the bottom of the meaning of the statement that if the same total amount of carbohydrate is consumed, then "sugar does not raise blood glucose levels any higher than starch". What it seems to mean is that the total amount of glucose that reaches the bloodstream is the same for a portion of sugar and a portion of starch that contain the same amount of carbohydrate - the body does not distinguish between the glucose that is derived from digestion of sugar compared with the glucose derived from the digestion of starch. But sugar is digested faster and reaches the bloodstream quicker than starch, so produces a sharper peak in blood glucose post-ingestion, especially if in liquid form, even if the total impact on blood sugar (the area under the graph of blood glucose plotted against time) is the same for both curves. This post-prandial peak seems to be the most harmful aspect of glycaemic control in diabetes, according to the experts, and subcutaneous insulin isn't quick enough to deal adequately with a sugar peak.

Having said all that, the total amount of sugar in most foods we eat is usually less than the total amount of starch - compare a serving of honey (1 tbsp = 15g) with the serving of bread (1 slice = 40g) that accompanies it. Even with bread at 50% carbohydrate and honey at 85%, you're still getting a bigger hit of starch than sugar overall. So having a little bit of honey on your toast isn't too bad, but drinking non-diet Coke is not advised. Except to treat a hypo.

The next stage in the module, after I've properly consolidated what we learned (more formally than just writing a blog post), is to find myself a case study and start writing it up. We have another two days taught in July including an assessed presentation, then the case study has to be ready in October.

There will now be a short break while Mr A and I go on holiday...

Carbohydrate reference tables

Leamington Spa, March 2013

People with diabetes who take insulin can do so in a number of different ways. The most common regimens are either a twice-daily injection, a fixed basal-bolus schedule of four injections, or basal-bolus with 'carb-counting'.

The twice-daily injection is 'mixed' insulin, where a proportion of the shot is long-acting and the rest is short-acting insulin. The amount is fixed, so with this regimen it is important to eat regular amounts at regular times, because if you skip a meal or a snack or don't consume enough carbohydrate, you can experience low blood glucose - a 'hypo'.

The fixed basal-bolus regimen consists of a daily shot of long-acting insulin, and three fixed injections of rapid acting insulin, one with each main meal. This is a little bit more flexible than using the mixed insulin, because you can tweak it a little by adding in or omitting some extra rapid-acting insulin as a 'correction' to pre-meal blood glucose levels that are too high or too low. It is still necessary to eat regular and consistent amounts of carbohydrate.

'Carbohydrate counting' is the most flexible option, where you still need the once- or twice-daily long-acting insulin, but you match the rapid-acting insulin to the amount of carbohydrate you eat. It allows you to skip meals, eat extra meals, eat early or late, and eat as much or as little carbohydrate as you want, but in return you have to do some work. In order to match carbs and insulin, you have to estimate how much carbohydrate is in your food, convert that to units of insulin, sometimes add in or take away a correction dose, and that's what you inject.

Estimating carbohydrate content of food can be done in a few ways. Food labels are the best estimate, as long as the food has a label and you can work out how much of it you ate. A whole margarita pizza is 337g and the label says it contains 29.1g carbohydrate per 100g, and you ate about a third of it with salad - call it 30g carbs. But if you cooked six handfuls of raw macaroni and added tomato and cheese and shared it with your partner who ate a bit more than half and there's some left over, and the macaroni packet says there's 73g of carbohydrate per 100g raw macaroni and the tin of tomatoes is 400g at 3g carbs per 100g, and then you had a medium apple, then how much carbohydrate did you have?

There are now pictorial guides and smartphone apps that will help you to estimate visually how much carbohydrate is in various foods, but they cost money, and many people don't have smartphones either. So we give patients carbohydrate reference tables that we have compiled ourselves.

For historical reasons, our hospital has two different carb reference booklets. Neither is particularly comprehensive, and I have some major concerns about their inconsistency. I don't much like either of them, so when it was suggested that I take over the project to bring them together in a single updated version, I thought that would be a great idea.

I have spent a lot of time on four different supermarket websites. They are great; nowadays you can find out all sorts of nutritional information without actually having to pick up a packet of food and look at the label. I am discovering some interesting things - for example, the carbohydrate content of sliced bread is a common starting point, and it's easy to remember that a thick slice is about 20g carbohydrate, a medium slice is about 15g and a thin slice is 10g. What I discovered in my 'research' is that supermarkets no longer offer thin sliced bread. Who knew!

I've also been using the pictorial guides, and the Bible for nutritional information: McCance and Widdowson's The Composition of Foods (Sixth Edition) which contains not only the carbohydrate content but a million other details of the nutritional composition of almost anything edible that you can think of. I must be about a third of the way through the job of revising the tables, and there are some interesting questions that I'll take to the team for a decision. For example, I think we've already decided that, unlike previous tables, we won't be rounding the figures to the nearest 5g. But how many different breakfast cereals should be included, given that cereals always have labels with nutritional information? Should we bother to include any cereals at all?

It's an interesting exercise, it's useful for me to focus on carb content of all sorts of foods, and a handy task to have when patients don't turn up for their appointments. I'm looking forward to having an agreed final version that we can all trust.

Pumping insulin

October 2012

In the early days of insulin-treated diabetes, people with Type 1 diabetes used to draw up insulin from a vial and inject using a hypodermic syringe. Nowadays, most people use 'pen' devices. These have a pre-filled insulin cartridge, a way of 'dialling' the number of units of insulin you want to inject, and a very tiny thin needle, which can be as little as 4 mm long. [Note: the linked website made me chuckle with its description of one of the insulin pens as "designed for people who don't like needles and children."]

However, today's blog is about one of the newer developments in insulin delivery, the insulin pump. This consists of an insulin reservoir containing rapid-acting insulin that provides continuous subcutaneous insulin infusion, 24 hours a day, via a cannula inserted into the skin. Most insulin pumps have a tube between the reservoir and the cannula, but there are tubeless types as well. The cannula can stay in place for two to three days. You can safely disconnect for about an hour, for showering, sports, trying on clothes etc.

For those of us who don't have Type 1 diabetes, our insulin level is adjusted minute by minute in response to all sorts of hormonal signals, such as levels of adrenaline, cortisol and growth hormones as well as the amount of blood-borne glucose. To imitate the insulin-secreting action of the normal pancreas, people on multiple daily injections (MDI) inject two types of insulin: long-acting once or twice a day, which is designed to release slowly into the circulation over a period of around 24 hours, and quick-acting insulin that lasts about 4 hours, injected at mealtimes to deal with the glucose entering the circulation from the carbohydrates that are eaten.

Like the human pancreas, an insulin pump only has one type of insulin, but two separate ways that it is delivered. There is a background or 'basal' rate that delivers the constant low-level drip of insulin day and night. At mealtimes, the pump user still has to decide how much 'bolus' insulin to give and at what rate - the pump doesn't remove the need to test blood glucose and calculate the carbohydrate content of food, and the injected insulin still doesn't act as quickly as insulin secreted by the pancreas directly into the blood circulation. But there are advantages to having more control over the amount of insulin going in.

For example, the basal rate can be adjusted on an hourly basis, and some pump manufacturers set up their pumps with a variable basal rate to match the general circadian pattern found in most people. A pump can also be of great benefit when exercising or drinking alcohol, because both of these activities tend to lower blood glucose, and it can be frustrating to have to take extra carbohydrate in order to avoid a hypo, especially if you're trying to lose weight. With a pump, a temporary lower basal rate can be set. [Note: exercise with diabetes is a fascinating physiological puzzle that I've been trying to figure out for the past few weeks, and I'm sure a blog post will appear on that subject very soon.] If you're on a once-daily injection of background insulin, then you can only adjust the background rate over a period of days.

There's lots of flexibility with the bolus insulin too (which could almost be done with MDI if you were prepared to give several extra injections). Many people find particular foods take ages to digest, especially if there is a lot of fat mixed with the carbohydrate (pizza is a typical example). If they inject just before or just after the meal, the rapid-acting insulin deals with the first surge of glucose but then its period of action is over before the food is fully digested, and their blood glucose level drifts upwards. With a pump, you can program the meal bolus to be delivered either in multiple bursts (just after the meal and then 30/60 minutes after or whatever) or at a constant rate over a period of time. This also works for really long meals, like a posh dinner with big gaps between courses, or for buffets and parties where you might be grazing over a long period of time.

Other advantages with the pump: it can help you with the sums, so you can be more accurate with your insulin dosage. For example, if you have calculated that your meal contains 48 grammes of carbohydrate and your ratio is 1.8 units of insulin per 10 grammes of carbs, the pump can do the calculation without blinking and deliver fractions of a unit (8.64 units in this case). On MDI, everything would be rounded off because we don't hold 1.8 times tables in our heads, and most pens can only deliver whole units of insulin (50 g carbs at 2 units/10g = 10 units of insulin). The ratio of insulin to carbs may change through a day (many people are more insulin resistant in the morning) and that can be programmed in to the pump software. And if you tell it your blood glucose reading, it can also suggest a correction dose, which can even take account of 'insulin on board', i.e. any insulin previously injected that may still be having an effect.

Of course there are disadvantages, not least the cost of the pump, which is available on the NHS only for those who meet the funding criteria. There's the inconvenience of wearing the pump at all times, which can place limits on clothing: at the beach, or on special occasions (e.g. with a party dress). The most worrying to me, based on what I've seen of patient care for diabetes in hospital, is that with a pump you have no long-acting insulin on board, and if your pump is disconnected for any reason your blood glucose level will start to rise after just an hour or two. If this happens at home, perhaps because of a blocked tube or kinked cannula, you should spot it and be able to deal with it. In hospital, the general awareness of diabetes is fairly minimal, and knowledge of insulin pumps is non-existent. There might be a risk of not being given insulin because it is assumed that you will have some level of background insulin on board, and that could have serious consequences.

Where I work, there are special clinics for pump patients, and I attended one of the monthly education sessions where pumpers can drop in to catch up on particular aspects of treatment. My colleague RSB is covering the pump clinic at the moment, so I don't yet have much contact with this group of patients, except for Mr M, who is a pump user, and who is always happy to enhance my knowledge of the issues.

[Update: Mr M informs me that contrary to my assumption, the first wearable insulin infusion pump was invented by Dean Kamen in 1970, while the first insulin injection pen device was introduced and marketed by Novo Nordisk in 1985. Thank you, Mr M!]

Counting carbs

October 2012

I am still on my own at work, and it's not going too badly. I like the job more every day, and my steep learning curve continues. I feel privileged to read and hear the accounts that patients share with their doctors,  nurses and other healthcare professionals, even if they are not complimentary. Patients are angry, sad, depressed, anxious, overwhelmed or struggling, and luckily for my state of mind they are occasionally happy, positive, grateful or just demonstrate a very welcome sense of humour. They are always interesting, and sometimes interested.

I am now working with several patients on carbohydrate (carb) counting, which means that the patient estimates the carbohydrate content of everything they eat. I try to start with a brief description of digestion, then ideally find out what the patient tends to eat on a typical day. This allows me to understand their choices a bit better, and tailor the rest of the consultation to suit that person - for example, if the usual diet contains couscous and tofu, I might go about things differently compared with pie and chips.

Carb counting is usually something that adults with diabetes tend to learn after they've been diagnosed for a little while, a few months at least (although there are exceptions). So they ought to know already which foods do and don't contain carbohydrate, although it always pays to check their knowledge at this stage. Even within my short experience, I've found a surprising number of people who have been choosing their insulin dose according to the quantity of food on the plate, rather than considering only the carb-containing foods. For example, a very large cooked breakfast including bacon, eggs, sausage, black pudding, beans, mushrooms and tomatoes with a mug of tea with a splash of milk contains very little carbohydrate, and the amount of fat and fibre in the meal means that no quick-acting insulin needs to be injected.

So we establish appropriate knowledge of carb-containing foods, then move on to quantifying the amount they contain. I can provide different types of written information, and we have food models, pictures of food on plates and packets of food complete with nutritional labels. Then I can refer back to the typical day's diet, so the patient can have a go at estimating the carbs in their typical day. That's the first stage, and sometimes that's all that happens to start with. The patient goes home, and for a period of time just estimates the amount of carbs in their food without changing anything else.

The next stage is to apply this knowledge to insulin dosage. Essentially, to maintain good levels of blood glucose, carbohydrate intake and rapid-acting injected insulin need to be closely matched. This is a simple statement, but it's never that simple. There are different insulins, people react differently to the same food. Other factors impinge - stress, activity, alcohol, hormones, medications, illness, previous dietary intake, dosage of long-acting background insulin, the sex and size of the patient, previous blood glucose readings, injection sites, quality of insulin, quality of injection devices - there are a myriad of possible factors that will mess things up. But to start with, we work with just a few numbers.

At this second stage, having checked whether the patient's carb estimation is reasonably accurate, they might choose to start adjusting insulin dosage. This is done using two ratios: the amount of carbohydrate that is matched to a unit of insulin (or vice versa), and the change in blood glucose level that can be brought about by a unit of insulin. There is also a target range of blood glucose that people aim for, which is chosen individually and may depend upon the time of day - let's say for the sake of argument that it is between 5 and 8 mmol/L. We will further assume that the background insulin is at the right level, although this is an assumption that can rarely be made in the real world.

The patient tests blood glucose before a meal, and estimates the carb content of the meal. If the pre-meal test is within range, then the insulin to carb ratio is used to calculate the amount of rapid-acting insulin to be injected. For example, if the ratio is 1 unit to 10g and the meal contains 50g of carbohydrate, then 5 units of rapid-acting insulin are needed.

If the pre-meal test isn't within range, then a correction can be applied. If the pre-meal test shows blood glucose is high, then extra insulin can be given, and if low then an amount can be deducted. For example, if the pre-meal test is 15.2 mmol/L and the correction dose is 1 unit to 2 mmol/L, then 3 or 4 extra units of insulin will be needed along with the insulin to match the carbohydrate in the meal. If the pre-meal test is 4.3 mmol/L, then one fewer unit of insulin might be given - 4 instead of 5 units for a meal containing 50g of carbohydrate.

In an ideal world, this would result in a relatively steady blood glucose level that may rise immediately after a meal, but would return to within the target range by the time the next meal is due - no higher, and no lower. A higher blood glucose may make the patient feel ill, and increases the risk of diabetic ketoacidosis and long-term complications. A blood glucose below 4 mmol/L may make the patient feel ill, and needs immediate treatment to mitigate the risk of hypoglycaemic coma and, in the worse case scenario, death.

Together with a specialist nurse, this week for the first time I helped a patient to start carb counting. The nurse prescribed the insulin, but I suggested the ratio and correction dose. Ever since that consultation I have been worrying that my advice was flawed, to the extent that I have been trying to contact the patient to check that all is well. So far, I haven't managed to get in touch, and all I can hope is that if anything had gone wrong, the patient would have contacted us.