Anaerobic Highs?

Has anyone experienced high sugars following running races during which you are pushing yourself beyond aerobic limits? My last two Bolder Boulder 10K races have been followed by anxious hours of high blood sugar, followed by over-compensated BG crashes. I’d like to have some means of preventing the fly-high-and-crash phenomenon the next time I run hard in a race. I run with a pump ( Animas IR1250 ) and have considered raising the Basal before the race. The fear is that I will over do it and go crazy-low during the race. If anyone has the perfect program, I’m all ears!

I’m not sure about the physiological mechanism that causes highs after physical exertion, but it used to happen to me. There’s plenty of info on the web about why it happens.

For me the issue was that I was turning off my pump. Instead I should have been decreasing my basal an hour before and for the duration of the run. That stopped them.

It doesn’t sound as if you’re stopping your pump, but I certainly wouldn’t recommend increasing the basal. Have you read “Pumping Insulin” by John Walsh or “the Diabetic Athlete” by Sheri Colberg? Both good resources for pumping and exercising.


Hi Terry-
I have read the Colberg book, but not the Walsh one. Can I ask what kind of sport you’re into? I’m a cyclist/runner, and occasional swimmer. To call me a swimmer would be a disgrace to the sport though ! My endo theorized that the reason for my post-race highs was that I was running hard in the morning after skipping breakfast, and breakfast bolus of course. Since I was running anaerobic and had nothing but basal insulin to counteract the adrenaline-induced glucose production, the blood glucose rose unimpeded. He thought that I then overcorrected, and the overcorrection coincided with the falloff in adrenaline and glucose-production. Those two effects overlapping produced the crash 3 hours after the race. I’ve not run a hard morning 10K since last May, but have run two hard morning 5Ks since. Both of those mornings, I took a small bolus and ate a corresponding small snack before the race. Post-race I was under 125 and never dropped below 80 in the 3 hours following the races. So that seems good at least for 5Ks. I did not twist the basal at all for either of those races. I’ll try a similar deal for the next 10K and see if it works as well at that distance.
Thanks for your suggestions, and happy running, biking, or whatever!

Hi Tom-

I’m a runner BTW. I’m training for the LA Marathon (Mar 2) but I’m sidelined with the flu yesterday and today.

the explanation offered by your endo sounds familiar. Although exercise makes our muscles more receptive to insulin, so that we need less, it doesn’t use up glucose, as I used to think. In other words, exercise helps the insulin, but its not a substitute for insulin. My mistaken belief there is what got me in trouble.

I diabetes trainer pointed out to me that non-diabetic runners do not turn off their pancreas, that the exercise and hormones have an immediate affect on my blood sugars, but that the insulin generally has little affect until it peaks 2HOURS later. She taught me how to mix these up to develop a safer routine.

For me (Your Mileage My Vary) I start a run, especially a long one, with elevated BG. Anything from 125 to 200 is okay with me, but sometimes higher. I generally eat a little something and reduce the bolus by one unit. I always eat something if my BG is between 80 and 100 and wait for it to crawl up.

If I’m running 30-45 minutes, I don’t change anything on the pump, but I always carry a monitor anyway to check after 30 minutes.

(Oddly, I find that my running feels more relaxed and efficient when I’m low. The better I’m running, the more likely that I’m low, probably because my mind is foggy and starting to drift.)

For a long run, I reduce my basal rate by 50% starting an hour before the run. The idea is that I’ve given myself a BG ‘cushion’ for the first our with the food, reduced bolus and slightly elevated BG. Remember, the reduced basal won’t ‘kick in’ until I’ve been running for an hour.

The reduced basal rate start an hour before the run and ends when the run ends. Here the theory is that the muscles are sill using up the BG on board and don’t need much additional help. The return to regular bolus doesn’t ‘kick in’ until two hours after my run.

So,this is working for me to prevent post-run highs and ketoacidosis episosdes. I haven’t had any unusual lows following a run (it’s during the run where I have a problem, even with the reduced basal - I always carry tabs, some gels and a mini-monitor). I am considering extending the reduced bolus to maybe an hour after the run for my really long runs.

More trial and error.


Thanks Terry. That’s a great, detailed description, and it does make a lot of sense to me. How often do you do finger-sticks during a marathon? Do you have a good way of carrying all your kit so it doesn’t get annoying banging around on your hips or whatever? I heard of a guy who works for Animas and runs marathons who actually tested BG while running. Are you able to pull that off, or do you stop briefly to test and take actions to correct lows? Seems like this is where a continuous monitor would be a great help, but for me, still not too appealing to have yet another device attached to my bod!
Thanks again, and good running to you!


I test every 30 - 45 minutes. I bought a small belt with a tiny pouch that holds my glucose tabs. I have a One Touch Ultra Mini which I attach and I wear it beneath my singlet to keep it from bouncing around. It’s tight enough that chafing isn’t an issue. I just have to keep it way from my insertion site.

I can test while walking, but not while running, although I’ve seen people do it. Either way it takes practice. I’ve also seen people testing while biking.

I also have a CGMS but find it unreliable during strenuous activity, mostly because it’s about 15 minutes behind the actual blood sugar. It can tell you how quickly your BG is going down, but don’t rely on the number.


Yeah, I totally start shooting up from anaerobic stress, I do this on a bike not my feet. And yes, don’t overcompensate because as soon as the stress is gone the insulin in your blood stream will drive you down down down. I have found my heart rate monitor gives me a good guess of where my sugar is going. I usually bolus instead of adjusting basal, easier on bike, but I guess it would make sense for you, though I think you only need the addition near the beginning of the effort if your body is like mine.

Hey Sarah-
Tell me more about how you relate your heart rate to where your sugar is heading. I’d love to be able to pick up on a trend there. I do a fair amount of cycling as well as running — especially when Boulder is calm, 50 degrees, and sunny in February!

Hi Tom,

I have the same problem. I never get to eat any of the post-race goodies because my BG is always high. While everyone else is munching on bananas, I’m dialing up a correction bolus and drinking water. My training runs are not like that at all, and if anything, I have to fight to keep my BG up. I don’t know if it’s the hormone release from the race-day excitement, or as you suggested the anaerobic effort. Either way, I have been too chicken to try to correct during a race. My races are pretty few and far between thus far, so I hate to risk not finishing due to a low. The highs come down pretty readily for me, and I don’t seem to crash afterwards. Please post if you try upping the basal rate and share your experience.

Just read the replies (should have done that before posting)…great info!