Exercise and Insulin Sensitivity

Hello All,

I am a 31 year old man, I was diagnosed just over 3 years ago. This is my first foray into an online community. While I have been learning the up’s and down’s of being a T1D for the past few years, this last year has been the most difficult for me (my honeymoon phase ended about a year ago i’d say), I’ve realized he importance of eating right and excising, but it is wreaking havoc on my insulin sensitivity. I typically run a mile or 2 once or twice a week, and on top of that I play basketball hard for 1 to 2 hours once a week as well. The issue arises after the basketball session. The next morning my body is extremely sensitive to insulin, I usually cut my bolus in half (this sometimes works), sometimes down to a third (sometimes works as well) of what it would normally be but that doesn’t always work, and I still find myself dropping incredible amounts in short periods of time. Just this morning my sugar was tanking after breakfast so I corrected (overcorrected in all honesty) and suddenly my sugar was 308, then I took a fraction of the correction my PDM suggested and within 40 minutes my sugar was 88 and going down fast!! Needless to say I have been yo-yo-ing since.

Wondering if anyone could offer advice, their own history with exercise and sensitivy, reading materials etc?

I use the Dexcom G4 and an Omnipod

Hi There!

I have to leave to go somewhere soon, so I can respond in more depth if you need, but I have been an avid runner/collegiate soccer player the last 5 years with T1D and go through the EXACT same thing (it actually has become more apparent as I have just started using the Dexcom CGM about 3 months ago). I would have severe night hypoglycemia after workout days, causing me to wake up in hot sweats, etc. If I made it through the night, I would have extreme insulin sensitivity as well, and actually stopped taking my breakfast insulin altogether (I also ate fairly low Glycemic index foods). The main changes I made: reduced my night insulin by 2 units (I am still on injections, so that might be different with a pump, but possibly decrease the rate of delivery?) and ate yogurt and fruit 45 min before bed each night (this is hard for some people, but I found that it helped me last through the night and keep my blood sugar up until the morning). There are few things to take into consideration as well–recovery and timing of exercise. Let me know if you want to know more about that! Hope this helps! Thanks,


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Sofie, thanks that was really helpful!

I don’t typically have a problem with my nighttime sugar after playing basketball, but I play from 7:30PM to 9 or 9:30PM so it seems to peak on me when I wake up in the morning (5AM) as far as I can tell. I’ll have to try NOT bolusing for breakfast next week, and then perhaps going low-carb for lunch and hopefully by dinner my sensitivity will have corrected.

How long does the added sensitivity usually last for you? Lately when this happens to me a tend to freak out and end up spending a couple days in the 200 - 300 range (not good), before I finally start bolusing normally again.

Over the holidays I wasn’t playing basketball but I was running 1 to 2 miles 3 times a week, I didn’t notice any real change in my sensitivity.

Anything you can add when you have the time would be appreciated thanks!


PJ exercise can change my sensitivity for 1-2 days. Regular exercise can change it permanently. Vigorous workouts every other day or every 3 days might be harder. Everything we do is a learning exercise. Test a lot. For me , my basal rate is what kills me when I am exercising more than usual. If you are trying to only adjust meal time insulin, in my opinion, you might make yourself crazy.

Good luck.

I have experienced the yo-yo-ing, and recently when I asked my new Endo, she told me that blood becomes more concentrated due to dehydration, which will result in it showing an artificial high. She has told me to drink lots of fluid to hydrate, and the blood will thin resulting in more accurate numbers. The blood sugar can be very far off due to this. I’ve seen 300’s, but when I was hydrated about 30 min later, without any insulin my number was actually in the 140’s. Its a good point to discuss with your Endo.

Are you reducing your basal pre and post workout? I change my basal to 0% up to 40 minutes before a workout, leave it through and then at least 30 min past the workout. I know that’s not sensitivity exactly but I wonder if leaving your bolus on lets the sensitivity increase new insulin is pumping in. I know my sensitivity goes up if I take a hot shower! It’s such a guessing game…