Risks of Marathon Running and Hypoglycemia in Type 1 Diabetes


A friend of mine sent me a link yesterday to an article titled Risks of Marathon Running and Hypoglycemia in Type 1 Diabetes with a note, “please be careful!!”. At first I dismissed it, as I often do when I get unsolicited advice, but as the article was published by the US National Library of Medicine and my friend happens to be a doctor, an endo, no less, I decided to take a look and see if there was something to learn.


The article is a case study of a 27-year-old man with type 1 diabetes who, despite suffering an extreme episode of nighttime hypoglycemia (which provoked a tonic-clonic seizure), decided to run a marathon the following day.


Running and Hypoglycemia

During the marathon he collapsed with severe hypoglycemia and had another seizure. He subsequently developed severe muscle pain (myalgia) accompanied by a pronounced and persistent elevation of plasma creatine kinase, indicating rhabdomyolysis, and deranged liver function, suggestive of hypoxic hepatitis. These symptoms lasted for several weeks after the race.


I don’t know exactly what these complications are but I got the point – people using insulin should not undertake prolonged intensive exercise after severe hypoglycemia.


I know this may sound obvious, and it would be easy to dismiss the guy as an idiot, but I hate to tell you how many times I’ve gone running after a nighttime low followed by a rebound high. What usually happens in these cases is that I wake up in the 200’s go running, and then find myself crashing after 2-3 miles.


Although I know my blood sugar levels tend to drop quickly after nighttime hypoglycemia, especially when exercising, I don’t think twice about it and stick to my plan. This is true, while training for a marathon or just running for exercise (although I’m usually training for a marathon). I have called off some runs after a severe low but I have to admit that I probably wouldn’t give up a marathon if I had suffered a low the night before.


After all these years of running with diabetes, I’ve learned to check my blood sugar two miles into my runs, expecting my blood sugar to drop. Nighttime lows are different, though, and they can offset everything the next day.  On an average day my blood sugar will drop from around 140 to 90 during the first 2-3 miles of a run. But on a post nighttime low I can start in the 200’s and find myself 2-3 miles down the road trying to treat a low somewhere in the fifties. Another thing the tends to happen to me after a nighttime low is that even if I catch myself in the 70’s or 80’s, I need to take another gel two miles later. There have been times when I’ve had to stop running after a few miles because my blood sugar just wouldn’t stop plummeting.


At this point you may ask yourself why I would ever go out running after a low. There are two parts to the answer. The first is my need to keep on going, stick to my schedule, and not give in to diabetes. The second is that things don’t always go so wrong. Sometimes all that is needed is an extra gel and I find myself having an excellent run. I imagine that this has something to do with the severity of the nighttime low and probably other factors, too.


Another problem is that I’m not always aware of the nighttime lows since apparently thanks to gluconeogenesis, many times I wake up high (or at least I did until I started taking metformin).  I don’t know if it’s a rebound or just a regular morning high until I’ve gone running and crashed.


Until now, though, I’ve considered nighttime hypoglycemia and its effects obstacles to my running schedule, I did not consider them a dangerous situation I needed to avoid. Maybe it’s time to think less about my running schedule and my weekly millage and more about the serious effects and dangers of hypoglycemia so I can continue to live and run for many years. 

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10 years ago

Ok. Just posted a comment over on Catherine’s post about exercise and our daughter wanting to run cross country. Hadn’t even considered factoring her nighttime BGs into the equation. Having read that list of complications now, it sounds like I might be timing my own runs with middle school cross country next year. 

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