High BG after AM Workouts

Hi there!

I am an active 25 year old pump user who usually workouts about 3 times a week always in the evening after work or on weekend afternoons. I’ve decided to try and go to the gym in the morning before work in order to make it more likely that I’ll workout (I’m shooting for a 5 days/week average and evening plans always conflict with working out). I have gotten pretty good at managing my sugars around my PM workouts but when I switch and do the same workout (mainly cardio with a little bit of weights) in the morning I go high. I’ve done a fasting check of my AM basal and that’s good so it’s not a misdosing for the dawn effect on a daily basis.

This morning for example:
pre-workout - 158 (higher than I like due to a late night high last night that clearly wasn’t properly corrected)
no temp basal, no food, no bolus
immediately post workout - 218

I’ve been reading around and people have mentioned the dawn phenomenon as an explanation - that the cortisol your body churns out in the morning as a normal part of getting you started for the day can raise your BG. But why would exercise cause the cortisol to have more impact than on a non-exercise morning?

I’ve also read that it is due to the liver releasing stored glycogen. But it’s not happening with the same workout in the PM (or at least not to the same extent). What about the AM would cause the liver to release more and in the PM?

I am trying to understand the precise biological mechanisms at work here and any insight you might have would be much appreciated.


Hi Wanda and Welcome!

Looks like I’m not alone. Check out my post last week on this very topic. I got a lot of good feedback too…


In a nutshell, it’s not an exact science. Beginning a morning exercise routine can be tricky, and frustrating. Some people just end up quitting a morning workout because of the adverse affects on the blood sugar.

I’ve been on the morning routine for about two weeks now. Every single time I worked out, I got the immediate morning spike. It wasn’t until today that I finally got a smooth reading. Woke up at 127. Took 2 units of Humalog (I usually take this just to cover the dawn phenom) and a protein shake (3g carb). This time I didn’t go nuts on the cardio, just about 5 min to get the heart rate up, then weights for 45 min. Cruisin around 105 all morning, no extra shots. Joy!

This is the most frustrating part of my diabetes right now, as I am trying to get my insulin sensitivity up and my A1C down. Don’t let it get to you and keep trying to figure it out. I really don’t want to quit my morning routine either because it really helps my blood sugar overall, but I might have to change up my workout schedule if it keeps hurting my morning numbers.

Good luck and keep me posted if you figure anything out. I’m in the same boat right now and I hope we can help each other figure this out:)

I had read your post. It was actually what popped up when I searched google when I got to work after my morning workout. This isn’t the first time I’ve had this happen but it was the time that I was finally motivated enough to start searching around for some answers. I’m glad to have found this online community to help puzzle with about the mysteries of diabetes.

I just wish we could find a definitive biological/anatomical/hormonal answer about why this AM spike happens. I’ve always found that understanding the underlying mechanisms helps me deal with the difficulties of a diabetes predicament.

Next time I will put aside my fear of workout induced lows and try a little bolus and see what happens.

Thanks for your encouragement!

I have been lifting weights at they gym with a trainer in the a.m. once a week and my blood sugar always goes from normal to over 200. Last week I finally increased the basal rate on my pump to see if it would help. Last week I increased it to 125% for 1 1/2 hours, but I can’t remember now what my blood sugar was. I think it was still high. : (

This has been my experience as well. Before I started triathlon, I ran about 6 days per week. I would leave my basal alone and usually drift up a bit by the end (without eating anything). My basals were probably set in such a way to keep things pretty steady. But if I increase the intensity of a morning workout, as long as I don’t have a lot of insulin on board, my BG will increase even more, sometimes dramatically. I think most people are less insulin sensitive in the morning to begin with, so you might need more insulin to cover the released glycogen (which is presumably happening) than you would later in the day. I don’t think there are any studies that show precisely what is going on in diabetes though. Perhaps it has something to do with “fasting” all night while you sleep; the body releases more glycogen because there isn’t much food coming in??

I now increase my basal from about 0.7 U/hr to 0.9 U/hr a couple hours before my morning workout. This allows me to eat a snack before I start without going high. Of course there are many factors that might affect whether I would increase (or even decrease) to another level; two major factors are how depleted I am from previous workouts in the week and what type of activity I am doing.

I try to eat a bit during my workouts because I feel better and can work harder. Then I try to restrict calories at other times for weight loss. When I am not having a gazillion hypos a day, it works pretty well.