Controlling Post-Exercise Highs

Any type 1 diabetic who has intense exercise as part of their regular routine has more than likely had to deal with a FRUSTRATING post-exercise high. I personally find the post-exercise highs very hard to deal with. It seems to fly in the face of everything that your doctor/CDE tells you should happen. Exercise is supposed to cause a decrease in blood sugars for a variety of reasons, and it DOES. Oftentimes, you may struggle with keeping your blood sugars normal through an entire workout, and then in the hour afterwards watch your blood sugars spike (not climb, SPIKE) up to the 300’s! ICCCKKKK!

When I initially started having this problem, I went to my doctor and I asked for advice. She advised me to not completely shut off my pump while working out and to not lower my basals as much before working out. Sounds great right? Except that when I followed her plan, my blood sugars bottomed out. I had to shut off my pump to run, and I had to lower my basals extensively beforehand to be able to run, or risk severe hypoglycemia. So what do I do? What do you do if your doctor can’t even conjecture much as to why this happens? I did some pretty extensive research on this subject (mostly on the internet and asking questions of other more experienced type 1 diabetic athletes, so don’t get excited, this is no clinical/scientific research I pulled off) and I’ve learned some pretty fascinating things concerning what I believe is happening. I’ve narrowed this phenomenon down to four things that seem to be the root cause of my post-exercise highs.

The first of these concerns carb replacement during a workout and the body’s ability to absorb all of those carbs during intense exercise. It has been shown that your stomach’s ability to absorb food during intense bouts of exercise is greatly reduced. That means you are replacing carbs to keep your sugars up, but your body just cannot absorb them all nearly as quickly as you are putting them in. That means that when you are done working out, your stomach quickly regains its ability to absorb carbs more quickly, and WHAM you have a nice high blood sugar on your hands! I have noticed, personally, that on days that I had lower sugars and had to replenish my body with more carbs than other days, I had a healthier (read higher) blood sugar than normal in the hour after exercise. The main thing I can recommend to combat this is DRINK MORE WATER!! And if you can, drink the water as cold as possible! Cold water aids in absorption, so hopefully you will absorb more of those replacement carbs when you need them, DURING exercise!

The second of these is ketones. Your body releases ketones when you are burning fat/muscle rather than available carbs in your bloodstream. The possibility of this happening was actually brought to my attention by Scott over at Scott’s Diabetes Journal, and I was so intrigued by it I had to test it out on myself! Sure enough, after an especially long and hard workout, I had quite a bit of ketones! I’m actually amazed that this isn’t something my doctor hasn’t brought up as it sure drives home what I try to enforce anyhow when working out: DRINK MORE WATER! The presence of ketones will make you resistant to insulin, helping to feed that high you may already be heading for because of unabsorbed carbs! Hopefully this will help to reduce those ketones in the blood stream. Do not let yourself get dehydrated during a workout; the highs are rough to recover from!

The third thing I’d like to touch on is the reduction of insulin in your body in preparation for a workout. In general, most type 1 diabetics on a pump reduce their basal insulin in the time preceding a workout. Depending on the time of day, I greatly reduce my basal insulin for 1-1/2 to 3 hours before exercise. I then shut off my pump during exercise. This works GREAT while exercising. This practice helps to avoid lows during exercise, when your body is so much more sensitive to insulin in the body. However, basal reduction before and during exercise doesn’t address the first hour AFTER exercise when you have very little insulin in your body while your body is returning to normal insulin needs and may actually be insulin RESISTANT due to ketones. If this sounds like a catch 22 to you, well, ya, I agree! I’ve done a few things to help remedy this problem. I set a super high temp basal for the hour post-exercise (2u/hr) and if my post-exercise reading is high, I double my correction bolus. I am NOT recommending anyone do this, I am not a doctor! I will recommend, though, that you test test test after exercise to help determine what is really going on with your blood sugars after a workout. I used to test every 15 minutes for an hour and a half to see what was going on to try and correct the inevitable spike. I finally got to a point where I felt comfortable enough to add a bolus/basal combination to help combat these highs. I was very conservative initially, and I continue to be conservative. If I’m concerned about a low later, for whatever reason, I follow my gut feeling. Id rather run a little higher than bottom out. My doctor recommended that for my longer workouts I return my basal to normal near the end of the workout, or with 20-40 minutes remaining in the workout. I did this successfully for some of my longer runs where I would be out running for over 2 hours. I could start up normal basals about 30 minutes before the run finished, and then switch to the super basal (2u/hr) once the run was completed for the prescribed hour.

The fourth and final point I’ve found that affects that rise in blood glucose post-exercise is what I’ll call a “rebound high.” What happens if you have a workout where you are struggling with lows the entire workout, or you have a rather rapid drop in sugars, even if you don’t go low? This could cause your liver to release glucose, further exacerbating the previous three factors that contribute to a high! The best way to combat this is to avoid rapid drops and lows during a workout. I control my blood sugars with carb gel during workouts that last longer than 30 minutes and this helps to really even out my sugars. I cannot underestimate the powers of GU and how it has helped with my endurance training!

The main things I’ve done to help control post-exercise highs are:
1. DRINK MORE WATER (the colder the better!)
2. Tested my blood sugars every 15 minutes post exercise for up to an hour and a half to be able to more clearly see spike post-exercise
3. Set up a post-exercise basal rate for the hour post exercise (implemented as a temp basal).
4. Set up a special correction factor for correcting highs immediately after exercise.
5. Used carb gel to help keep blood sugars more level during a run.


I firmly believe that diabetics really can achieve the endurance exercise goals they set for themselves. I ran my first half-marathon at 27 years old. I had just quit smoking a year before, and I hadn’t worked out substantially for over five years when I started training for it. I’ve talked to type 1 diabetics who have run multiple marathons, and even diabetics who are triathletes. Diabetes makes things more confusing, and adds arithmetic to practically every aspect of your life, but it does not need to stop you from being as active as you feel you need to be! Diabetes can feel limiting and it can feel hopeless, but you can feel empowered as you overcome these feelings of being limited and expand your expectations to beyond that of even most non-diabetics.