Post Exercise Hypoglycemia Questions - Very Low 1 Day Afterward

Hi All -

I have not posted here for a while, but I have a very serious question!

My wife and I have been getting into bicycling a lot.
This weekend we did a ride on Sunday morning at 10:30 am.
It was a nice ride, lots of hills and I did not make the while ride.

We then did not eat lunch until about 2:30 pm after spending too long in a bike shop.

We went home, had a late lunch and a shower. Dinner was 2 slices of pizza and a beer.

All was good from a BG perspective. I have been a type 1 diabetic on a pump for a long time (pump 15 years, Type 1 for 43 years).

Monday, I helped my mother just out of the hospital after surgery. Missed a normal lunch and about 1:30 pm had a sudden BG crash. To the point where we needed EMTs and after the pushed 25 cc of glucose into my veins, I came back to life after about 40 minutes. Bad! Bad! Low in my book.

So what is going on? I have lost ~15 lbs since Feb. I have been bicycling ~1-2 per week, ~1-2 hours per time. This is the third serious low. My wife and I are quite concerned. What is going on?

Theories are:
1- Drug interaction with statin I started taking
2 - Due to weight loss, basals are wrong
3 - Delayed Post Exercise Hypoglycemia

#3 is the best hypothesis, but these lows happen very fast. I also can’t seem to detect them. Also I become belligerent and refuse glucose (2/3 of these lows). It seems like some of these occur ~24 hours after the exercise. The idea is that the depleted glycogen stores trigger a rapid drop in BG.

The question for the group is -
Anyone else see these kinds of lows?
What do you do to avoid this?


Hi Frank, you can imaging how much fun it was when I was a pretty good bicycle racer (1976-78) (when we were young) and even endocrinologists were guessing…

Not having time to check my reference books, some of these numbers may be off a bit:

  1. The total glycogen stores of a 175 lb athlete are about 3500 calories.
  2. While riding we deplete 300 - 700 calories per hour so we need to reduce basal rates.
  3. Fatigued muscles need much less insulin to convert BG to glycogen, so the post-ride meal bolus must be reduced.
  4. Replenishing the liver glycogen requires reduced basal to keep BG up.
    I have found if I reduce my basal Lantus from 10 units to 8 (while I’m riding a lot), I don’t have huge problems. A ride over 50 mi or 4 hrs will require a further basal reduction the night before to 7 or 6. The evening afterward I usually reduce it similarly.

I’m still trying to find the diabetic cyclists group which was so interesting on Wednesday. Keep in touch.