Running on Insulin

Running on Insulin - One Drop

Have you ever noticed that when you run, your blood sugar seems to go up? If you have type 2 diabetes, it might be a gradual spike, maybe one that you don’t even notice. If you’re like me and live with type 1 diabetes, you probably see an almost immediate and very sharp spike in blood sugar.

What’s going on here? Isn’t exercise supposed to lower blood sugar?

I ended my run today at a very steady 104 mg/dL, but promptly bolused! Why? I often experience a super high spike in blood sugars after running for distances less than 8-13 miles.

This is because I run with almost no insulin-on-board (IOB) and with a disconnected basal to avoid lows. This is simply my personal diabetes management regimen while running. But this means that the normal physiologic processes that happen after exercise are unmasked (if you have too much IOB or sometimes even just constant basal the insulin will cover for the spike, and you’ll never know). ⁣

A Physiologic Process Breakdown

What is a normal physiologic process? After exercise, all that lactic acid produced by our muscles gets circulated back to our liver, where it’s converted back into glucose.

This glucose then gets dumped back into our bloodstream to be stored in our muscles as glycogen, to later be used as fuel for the next time we exert ourselves. Muscles (especially during or immediately after exercise) are great at taking up glucose (they don’t even need insulin to do some of it). ⁣

So in people with functioning beta cells and glucose homeostasis, all of this works as it should -- the glucose levels in the blood never get too high because of insulin. In people who administer their own insulin exogenously (people with diabetes), it’s something we should be aware of so that we can avoid it. ⁣

Again, if you’re someone who exercises with plenty of IOB, you might not experience this. But I think that the post-exercise spike is a great example of how our bodies aren’t so different from each other at a biochemical level. The things that really dictates our experiences with what happens to our blood sugars are our choices, decisions, and management. We have a lot of power to control our outcomes. ⁣

Of course, there will always be some differences biochemically between individuals, and stuff we can’t explain. But those situations are just a tiny slice of the whole pie. Most of the differences in our experiences with diabetes are due to differences who we are as people, not in who we are as bodies.

I find the science behind this really reassuring. We can always control more than we think!

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Jordan Hoese, MD, MPH
Jul 23, 2020

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