Raising BG before exercise - more harm than good?

Hi everyone, I’ve got one of those New Year’s resolution-related questions for you.

With my switch to the pump and Apidra, I discovered that insulin actually works much better in body all of the sudden. So well that I continually bottom out during almost all cardio exercise of over 20 minutes or so. Running, walking, biking, rowing, all of it.

I’m not generally organized enough to know two hours before my workout that I’ll be heading into the gym, so about a half hour to an hour beforehand, I turn my basal down or off, depending on the exercise, and then I’ll usually eat about 20 grams of un-bolused carbs to get my BG up a little too. So far, the results are mixed, with lows still coming about half the time.

From my blogosphere research, I’ve found that many diabetics will pump their BG up to over 150 or 200 before starting on cardio. I’m wondering if these daily spikes will actually cause more harm than good. I work really hard to keep my post-meals below 140, so I don’t want to muck it up with an un-bolused peanut butter sandwiches before a run.

Any insights out there? Thanks, guys!

I am 68 and do not do any strenuous exercises. A tread mill for 30 minutes, twice per day at a 7.0 incline is enough for me. If the weather is good I walk outdoors for 3 miles with some hills, in an hour. I lower my pump basal to zero and run my blood sugar to 120 max. I test half way through my walk and eat glucose tabs if needed. I agree that raising the blood sugar very high before exercising may be harmful/ A rapid rise followed by a rapid fall in blood sugar level does not sound good at all, especially if it is repeated several days per week for an indefinite number of weeks.


I think it’s a good idea to raise your BG before exercise if you keep going low in the middle of your routine. How much to raise it, however, is a matter of degree and trial and error. (just like everything else we do to control our BG).

For me, I do NOT turn off my pump for exercise, although I used to. As an educator pointed out to me, no one else at the gym turns off their pancreas to exercise, why should you? The results for me were ketoacidosis after running, which stopped when I changed to simply lowering my basal.

Although I like to start with my BGs somewhat elevated, I don’t purposely elevate them for exercise. If I’m afraid I’ll go low, I eat something and reduce the bolus by one unit.

So, my answer is that I don’t think it’s dangerous unless the ups and downs are sharp. If it’s slowly up and slowly down i don’t see a problem. If you’re having frequent lows during exercise you might try reducing your basal even further without turning it off, and getting some sport nutrition bars or gels, or sports drink to consume while you work out.


Hi Terry. I always take my exercise in the afternoon. My basal at that time of day is only 0.5 units so if I turn that off it is not nearly enough soI have to eat enough to have a BG of about 120 before walking. Even after all that I can drop to 70 or so after 30 minutes and need a couple of glucose tabs. This routine might work for some diabetics but it has worked well for me for several months now.


Hi, Lizzie. I exercise almost everyday and don’t like to get my bg up too. So, I reduce my basal by 50% an hour before exercise. It works great for me!

Richard. Everyone’s mileage is different. the effect of turning off the pump will not show up for about two hours, which is the peak time of the insulin. Check your records and see if you BG is taking a sharp rise about two hours after you have turned it off. It was for me.

But I always say in these matters - whatever works for you!