(another) Exercise question, I wonder if others have similar issues

Hi All,

So I’ve been exercising for many years but lately have increased the cardio significantly over the last few months particularly in the late mornings.

I’m curious if anyone else has had repeated low blood sugars in afternoons to early evenings regardless of basal being set to zero in this time frame and many carbs being taken.

I’ve dosed immediately post-exercise to reload the glycogen with some fast acting carbs.

Thank you!


So it’s a few hours following the exercise?


Yes, around 5 hours after and lasting for 3 hours. I haven’t had this phenomenon before and it’s pretty remarkable how many carbs are needed to simply keep the number from plummeting without much insulin in the system. My approach to reload glycogen right after the workout is 6 units of humalog and maybe 50 carbs. Also have noticed some occasional blood sugar rises from cortisol during this time if there isn’t enough insulin.

Approximately 7:30-8 PM it’s time to get some insulin back in the system although sometimes additional drops can follow. Over the last few months the progress has been from having 45 minute zone 2 session a few times a week to around 100 minutes per session.

Do you think this implies more carbs and insulin are needed post-workout?

Back in my younger years I played water polo and had to go on shopping sprees at 7-11 after the practices to keep the BG up and maintain body weight.


It depends on the workout intensity and which muscles you are using. Most likely you are not completely depleting muscle glycogen, unless it is a significant workout.

But workouts can also be cumulative, so if you are doing it everyday, you will become more and more depleted.

It might be that the 6 units is too much. You might want to reduce the 6 units and stick with the 50 grams, but also continue feeding (and possibly injecting if needed) for several hours afterwards too.

And maybe taking a rest/easy day and seeing if the same thing happens on the day after you have had some rest.


Interesting, I had never thought of cumulative glycogen depletion. I had always considered it as a daily thing. This week is for recovery but it’ll be interesting to see what the training block looks like after. I’m still quite new to these volumes so imagine that it takes time to get acclimated.


It depends on which muscles you are using and how hard you are working.

As an example, you can burn up all your leg muscle glycogen on a 10 mile run, or you can use practically none of it, if you are going slow enough.

For the most part though, it is rarely all and it is rarely none. Most activities will use part of it.

But successive days (if we are not replenishing adequately) will eventually burn through it all.


The schedule has evolved a bit over time but the general impression I’ve gotten is that the zone 2 cycling fits in just fine with the weightlifting…perhaps for that reason I’ve been increasing the amounts steadily to a level that needs more fuel and addaptation. One idea I had was to reduce activity on rest day.

For the last few months I’ve held a similar schedule to this and increased the workloads slowly. Overall it seems pretty balanced and even though the BG has dropped, I haven’t felt particularly tired. Every 4th week is a rest week that cuts the efforts in half.

The weights sections have gone on for many years so not too much soreness or fatigue from that.


Squat-335x,385x,425x,445x,465x,465,385 x 3 pause
Muscle Snatch-155,155,165,165,175,175
Push Press-155,175,195,205,225,245,245


Cycling Zone 2 96 minutes


Front Squat- 245x, 275x, 295x, 315x, 345x, 347.5x, 347.5x
Bench- 155,245,275,295,300,305
Power Clean- 95,135,155,185,205,225,235

10 sprints 60 meters


Cycling Zone 2 100 minutes


Deadlift 155/245/335/425/445/500/500/500/
Boxjump 9 repetitions close to maximum
Pullups 10 x 1


Cycling: 40 min zone 2, 5 Intervals 3 min on (Zone 5) 3 min off (Zone 1), 5 min zone 2

0310 ----Sunday rest day

Cycling: 60 minutes zone 1


If you are on zero basal, it is unique to continue to drop for such a long time.

Perhaps you have slow insulin absorption from the post-workout bolus.

As long as you are not worried about weight gain, I would just snack more during the hours that follow.


Hi - I have had similar issues, in that sometimes when I exercise I have a sudden drop later in the day which seems completely out of the blue. I have been looking at as the exercise “kicking in” later in the day (although I don’t know why this would happen) but also wonder about delayed absorption of insulin. It has been a real struggle and I have had some pretty scary lows (in the 30s). I do not currently use a GCM or pump. I have tried the GCMs a few times and haven’t liked them, but may be ready to try again. Although this might help me with this issue, I did not find the GCM helpful with drops during exercise because of the lag time. I would appreciate your thoughts on all this!



Hi @jsich! Welcome to FUD!

What exercise do you do?

I don’t use a CGM during my exercise. For that I use a lot of BG tests before and during. But I think a CGM is helpful for when I am sleeping.

The drop later in the day could possibly be related to the exercise, or it could be something completely different. It depends on when it happens, and how you are doing your insulin, and getting the background details to figure it out.


I get the same weird results sometime, think it’s my

Hi Eric,

Prior to getting Type 1 at age 49, I used to mostly run…a lot. I did a did a lot of 5ks, a few marathons and then a 50k and then a 50 miler. Once diagnosed and put on insulin, I found it really hard to do more than 10-12 miles in terms of keeping my BS at a reasonable place, plus the stopping to check it every 30 minutes or so became a pain. I am currently recovering from an injury, so mostly using a spin bike for about 60 minutes a few days a week, with some harder intervals. I do strength training 2-3 days a week, but don’t have too much trouble with BS then. The other complicating factor (which i’m pretty sure you won’t be able to help me with) is hormone fluctuations due to peri-menopause which make my BS more erratic that’s it’s ever been. I have recently had some BS readings above 250, which is totally new for me. I tend to under-estimate because I fear the highs, but that ends up sending me low too often. Sorry to ramble, I just wish there wern’t so many variables here!