I am a 26 year old female who has had type�1 diabetes for five years with hemoglobin A1cs always under 7%, and I am a runner. I ran my first half marathon with Team Diabetes Canada last year, but have become very frustrated with exercise and blood glucose control. I find that my blood sugar may be great after a run, but then spikes (often up to 16 mmol/L [288 mg/dl]) a few hours later. I wear a pump and have been playing a lot with my basal rates to try to prevent this spike, but I’m having trouble finding the solution.

I find that I am best off if I raise my blood glucose to about 10 mmol/L [180 mg/dl] before a run to allow for some drop. I test every 20-30 minutes during a run and treat with glucose tablets, if I see a potential to drop too low. I usually finish with blood sugars of 4.5- 7.0 mmol/L [81-126 mg/dl]. When my blood sugar is at such a good level, I find it hard to take extra insulin, just in case it decides not to spike.

As for insulin levels, I usually drop my basal rate from 0.9 to 0.6 units per hour for two hours before the run, or I will drop too low during the run. Lately, I have been raising my basal rates to 1.2 units per hour for a few hours after the run, but perhaps this is still not enough.

Last night, I only ran 6 kilometers and ended with a 6.8 mmol/L [108 mg/dl] reading. I ate a small snack afterwards for which I normally would only take 1 unit of insulin, but I took 3 units, and two and half hours later, my blood sugar was 18.7 mmol/L [374 mg/dl]!

I find that these spikes are having a huge emotional impact. I feel like no matter what I do, I can’t get it right. Is this pattern common?

This post-exercise spike in blood sugar can be a very common pattern in athletes, particularly with fairly intense exercise such as you’ve described. The hormone-driven rise in blood glucose levels after intense exercise occurs in all athletes, whether they have diabetes or not.

You are certainly doing the right thing by patterning blood sugars and experimenting with changes in basal rates to compensate (with your own diabetes team’s blessings, of course). I can also understand your concern, and rightly so, in compensating with large amounts of insulin after a run. Corrections for elevations after exercise should almost always be conservative, due to the increased insulin sensitivity and increased glucose utilization that remains for hours after exercise.

With your current exercise basal rates, does your blood sugar rise in response to every run of equivalent intensity? Are you currently maintaining the lower basal rate ( 0.6 units per hour) during your run as well? If that is the case, perhaps you are seeing a “lag time” rise related to this previous reduction. You may wish to experiment with a return to your normal rate during or towards the end of your run. It sounds like the increase in basal rate made after the run is occurring a little too late to prevent that rise in the first place.

Some athletes have addressed this by always snacking prior to exercise, with a partial bolus for the carbs. For some, this seems to provide enough extra circulating insulin peaking after exercise, just at the time that hormonal rise is likely to occur. That approach may be an option for you as well.

The Diabetic Athlete by Sheri Colberg, Edward Horton may be an excellent resource for you in this regard. You may also wish to contact members of the Diabetes Exercise and Sports Association (DESA) for the experience of other runners like yourself. Most importantly, don’t give up. You will find a solution that works for you.

DMW