Running As A Diabetic

Diabetes 4
Tom during the 2017 San Sebastian Half Marathon (Photo credit:

Tom Bartlett lets us in on what it’s like to train and race as a Type 1 Diabetic.

“Is that a pager? I’m amazed anyone still has a pager these days.”

No, it’s not a pager – it is my insulin pump. Admittedly my pump model does look like an old pager from the early 1990s. I get asked the question from time to time, and I don’t mind at all, as it gives me a chance to explain a significant part of my life – that I’m a type 1 diabetic. I was diagnosed at the age of 6, so being a diabetic really is a part of me and I can’t imagine anything different.

In technical terms, the problem that causes type 1 is your pancreas producing little or no insulin.  We get round this by injecting insulin, or by having a pump that infuses it in through a cannula, a tube that goes into the body. Insulin, in basic terms, is the substance that converts carbohydrates in the food that you eat into energy that you can use or store in the body.

Type 1 diabetes is different to type 2, which can be thought of as your body becoming resistant to insulin. Type 2 is often associated with lifestyle factors such as unhealthy diet and insufficient exercise. The good news about type 2 is that by improving diet and exercise, sufferers can often see an improvement in their symptoms. Type 1 is caused by an auto-immune reaction which destroys the insulin-producing cells. No one is sure what triggers this but with type 1, there is no going back.

The major challenge that diabetics face, all the time, is keeping blood glucose levels within the normal range – typically quoted as around 5 – 7 millimoles per litre. If your level drops below about 4 you are hypoglycaemic (‘hypo’ or ‘low’). If it is above about 10 you are hyperglycaemic (‘high’). Managing blood sugar levels is even more crucial when running. If hypo, I feel tired, lethargic, weak, and struggle to keep running. If it is really bad, you can get tunnel vision or lose the ability to see and can even become unconscious. Being high is different – if it is short term you won’t faint but you can feel nauseous, tired, and lethargic. Having long-term high blood sugar is what diabetics must try to avoid most, as it results in damage to the body that accumulates and results in nerve damage and deterioration in eyes and feet.

Tom's insulin pump, often found doing a cameo as a 1990s pager.

The Challenges of Insulin On Board

I was feeling tentative, on the edge, and just trying to hang in there. My muscles had partly turned to jelly. “Thank you!” I said to a kid who handed me two jelly babies. They may turn out to be more important than the kid realises, I thought, as I ran through mile 9 on the Royal Parks Half Marathon in 2013.

Half a mile further on I saw someone lying on the ground getting help and wondered what had happened to them. Hopefully nothing serious.  Being a diabetic runner, it sometimes all goes wrong too. I had started the race with an acceptable blood sugar of 8, but I took 3 dextro energy tablets because I felt like it might go low. My intuitions were correct and my blood sugar steadily dropped despite eating the rest of the packet (totaling 42 grams of sugar) over the first 8 miles of the race. I had no more sugar with me and it was now down to luck as to whether my blood sugar would stabilise after 14 dextro tablets and 2 jelly babies or whether it would continue to drop, causing me to have to withdraw from the race.

How can it be that I needed over 40 grams of fast-acting sugar when running a race? The problem is running with “insulin on board”. As mentioned earlier, insulin breaks down sugar – one of its main actions is to remove sugar from the blood and store it in the liver and muscle cells as glycogen. This is the opposite to what you need when you are exerting yourself hard in a race – you need energy being released from stores into your blood, so it can be used by your muscles (and your brain).  If you have insulin on board, your body is merrily storing sugar, causing your blood sugar level to drop.

To complicate things further, the effect of insulin on board is magnified the harder you run, because it seems that the body’s sensitivity to insulin increases with exertion. My rule of thumb is that I am 4 times more sensitive to insulin on an easy pace run and up to 8 times during a long, hard event such as a marathon or 100-mile cycle race. Modern fast-acting insulins typically reach peak effect after about 2 hours and are ‘used up’ after 4 hours. Therefore, if you take insulin for a meal and then start running 2 hours later, you still have half your insulin unused, so when you become more sensitive to it through running, it is like taking an extra insulin shot! This increased sensitivity is also important to consider when eating during long races. For example, when not exercising I would normally take 3 units of insulin for a Clif bar, but if I ate the same thing during the 100-mile RideLondon race I would only take 0.4 units and that would be sufficient to keep me level.

Diabetes Control During Races

At a wide, smooth section of the course, a runner moves to the side and slows down. He grabs some water from the drinks station and pours it onto his hands. He produces a small machine from a pouch on his waist. He makes his finger bleed and touches a small strip to the blood. He then struggles in the bright sunlight to read the display on a small pager-like device.

This is what someone would see if they watched me during a race and observant fellow runners probably do wonder why there is a guy is ‘doing funny things’ while he’s running. During a marathon I run with both my insulin pump and my blood sugar testing kit because it is too long and hard a race to judge my blood sugar just on the basis of feeling. I will test my blood sugar every 20-30 minutes during the first 2 hours and take a small amount of carbohydrate or very small doses of insulin, as appropriate, to push my blood sugar in the right direction. After 2 hours if I am feeling good and my levels are more or less stable I will then run on the basis of feeling, only testing if and when I feel dodgy. The washing hands with water is to avoid having results contaminated by glucose that might be on my fingers from handling dextrose tablets or other food.

I would love to know what it is like to race as a non-diabetic. It seems like you could just ‘turn up and go’. As a diabetic runner, I feel like more than 50% of the preparation is related to diabetes control. Perhaps that is not surprising: Barts Health NHS Trust leaflet on Exercise and Type 1 Diabetes, (click to download) for example, lists 12 different things you need to factor in when exercising.

In diabetic terms, the overriding objectives when racing are to arrive at the start line with blood sugar at an acceptable level and without any significant amount of insulin on board; and then to manage your blood sugar level within an optimal range, not too high or too low, during the race.

For any major race the diabetic planning starts with the training. During training I will test out how much insulin I need to counteract any carbohydrate intake such as Lucozade sport. I will also practice doing blood sugar tests whilst running. On training days or before races up to half marathon length, I do not eat before running, to avoid having any insulin on board – getting up at 4.30am to eat just doesn’t seem to happen on Sundays before a normal long slow run.

However, on marathon day I will make the effort to get up early and eat breakfast 4.5 hours before the race. A major race day is further complicated by the inevitable adrenaline rush before the race start, which causes a big spike in blood sugar. Experience has taught me that I should only take a small corrective, as blood sugar will come down quickly when you start running.

Shorter races present a different challenge – for example after doing a 10k or the Club Handicap, I usually get quite high blood sugar. This is probably explained again by adrenaline, and a general lack of insulin in my body as I turn the pump off an hour before racing to avoid going low during the race. So, perhaps counter-intuitively, I normally take a shot of insulin after finishing a short, fast run.

When I first started doing longer races, like Half Marathons, the challenge of managing my blood sugar was definitely the major limiting factor in my performance. Now that I have more experience, it feels like there is more or less an equal weighting between training and diabetes control. If I train well and get my blood sugar control right, I should be able to run fast. I don’t dream of being a non-diabetic, but I do dream of ‘nailing’ both my training programme and my diabetic control, and then running a brilliant marathon. Unfortunately, there is always luck involved in getting the latter right, because multiple factors can throw your control out – the main one for me is the varying absorption of insulin depending on where my insulin pump cannula is ‘plugged in’.

“Does being a diabetic stop you doing anything? It doesn’t really, right?”

I used to just blithely agree when people asked me this. Recently I’ve become more realistic – managing diabetes is a challenge. It takes planning, time and effort and does definitely affect how well you can perform in races.

However, when all is said and done, I accept that I have this condition which challenges my running performance. Yes, it can be extremely annoying, and frustrating. Sometimes I try really hard to get my blood sugar levels right but they keep going low and I just have to give up the idea of any run. But I’m not a victim – I do not go around feeling hard done by because diabetes sets my running back. Although it is fun to be competitive with other runners in the club, I know that when I’m racing, really the only performances against which I should measure myself are my own.

It is great to be part of the Serpie tribe, which I have found very supportive and accepting. Inherently we are a bunch of people who don’t just want to spend our free time on the sofa watching TV, we actively seek out things that are a physical challenge, and I can see my diabetes as just one part of that challenge. No-one wants too much adversity, of course, but if there was zero challenge there would be no achievement and therefore no point. Challenge is part of what makes us. Perhaps that is why I find a natural fit within Serpies!

So, I love running, even with the challenge of being a diabetic. It’s good for me, just like it is for anyone, and I get the same buzz as anyone before and after a race. I still have plenty of times when it feels like my legs are made of lead or jelly. I just have more reasons to review why I might be feeling that way – perhaps it is ‘just’ low blood sugar coming on and perhaps I will be able to correct it!

Caveat: This represents my personal, non-scientific understanding of diabetes and my experience of living with it. It should not be taken as medical advice.

Tom Bartlett joined Serpies in 2014, which led to a big increase in his running, however he makes sure to maintain a pub-time/running balance. He is currently thinking about starting to train for another marathon.