Spike in Blood glucose level post gym

Hi all,

I am a 26-year-old Male and was diagnosed with TD1 last year. My blood sugar level temporarily spikes too much after a gym session. My doctor said that it happens due to hormonal changes due to an intense workout.
Is this sudden and temporary spike a problem in the long term? Has anyone dealt with the same situation?


Yes, quite understandable. At some point in your workout routine you went beyond aerobic exercise [which tends to lower glucose levels] to anaerobic exercising that very often pushes body glucose levels [BGL] high, including extremely high.

I’m not a scientist or medical doctor but can offer a simple layman’s explanation that your muscles are screaming for extra food [sugar] for fuel and your alpha cells signal your liver to release glucagon / glucose.

Be aware that extended or extreme activity could cause a drop in your BGL 12 to 24 hours after the exercise.

I have been experiencing the same thing since I was diagnosed more than a year ago.
We are all different and respond to stimuli differently. BUt you are not alone. It took me a while to suss out how to deal with my sugar spikes. What this tells me is I have a healthy liver :smiley:

My sugars spike during ANY exercise and it can last for up to 3 hours after finishing a workout. I do things like kickboxing, aerobics, spinning, weights, walks and runs. The only time I don’t need to compensate is for walks as they are liesurely and don’t seem to effect my sugars one way or the other.

I avoid carbs before a workout and I set my basal to 200% during my workouts. Sometimes I have to bolus to get the sugars down under 200, but for the most part I have figured out how I react to each workout and I compensate beforehand with a bolus. Even a run, which for most people will lower BG, will spike mine.

Having a CGM allows me to keep constant track of what is happening and having the pump allows the double basal rate which helps tremendously.

You’ll figure it out, but I doubt it is temporary, as you are who you are. Good luck with figuring it all out. I wish this forum were a bit more chatty as I’m sure there are many people we could all learn from out there! Let us know how you do!

Hey !

Thank you so much!

Hey !

Thank you so much!

Hope I helped!

Thanks for this. I am 45 years old and was diagnosed with TD1 6 months ago. Any medium to high intensity workout spikes my BG where the only solution I have found is more insulin. The benefits of excercise outweigh the negative - but is there any hope that it will help reduce the amount of insulin needed over time?

Hi Mary,

I am not sure if I understand your last question about reducing the amount if insulin needed over time.

I am a Diabetic Lifestyle Coach with a PhD degree in biochemical physiology, and have T1D for 20 years, so I will try to explain as best I can. Just for your understanding, I manage my blood glucose through a healthy and very active lifestyle (I ride 400-500 miles per week by bicycle), and I know what you are talking about when it comes to blood glucose spikes during a high-intensity workout.

Dennis J Dacey (he happens to have the same first name as I do!), was pretty accurate with his explanation. And so was Linda. Let me give you a little bit of scientific insight:
When we do low-intensity exercise, we hardly use any glycogen (which is a large molecule made out of thousands of glucose molecules); our bodies prefer to use fat and save the precious glycogen for “emergency” activities.

Both your muscles and your liver can store glycogen. When you do a high-intensity workout, the fuel that is readily available for your muscles is - of course - the glycogen that is stored in your muscles. But as these stores run out, your muscles start to absorb circulating glucose from your blood stream. This lowers your blood glucose and that gets noticed by your liver, which then releases glycogen from its own stores to regain the balance in your blood.

If you immediately jump into a high-intensity workout, your body also produces a lot of adrenaline, which triggers your liver to release a burst of glycogen into the blood, even before your muscles start to run low. If your liver releases faster and more of this complex glucose than you can burn, your blood glucose will spike. And since you’re T1D (like me!), you don’t produce any insulin to get that glucose back to where it came from. This means that you will have to inject insulin to get that circulating glucose back into your liver and muscles (or you have to keep working out hard until the glucose is burned up to fuel your exercise).

Just be careful not to over-dose with the insulin, as your body is also hyper-sensitive to this hormone when you are so physically active.

Hope this helps.

[edited by moderator]

Thank you so much! Giving me more to consider…

Uday and others,

I would encourage you to refer to the information in this link from the Joslin Center. This link provides recommendations that are simple to follow and are generally accepted by diabetes professionals. And check out the other exercise-related links that appear on the page.


One of the things to focus on in the Joslin Center link is the blood glucose level of 250 mg/dl. Read the recommendations carefully and try doing what they suggest. It may make quite a difference for you.

Personally, before I begin pushing/pulling/lifting/shoving for any extended period I check my BG. If it is over 160 mg/dl I consider whether there is a need to take an “adjustment bolus” to keep my blood sugar from going higher. If I have “active” insulin on board I am usually safe to begin exercise. If I don’t have “active” insulin on board then I stop and consider what is going on.

I also always check my blood glucose after an hour-and-a-half of pushing/pulling/lifting/shoving. More often than not (always?) it is headed low and it’s time for a snack.

You asked if BG rise secondary to exercise has long term consequences. It is more of an immediate concern than a long term concern. These “spikes,” and what is required to get them to come back down, can lead to a BG “roller coaster” effect that can leave you feeling tired-to-exhausted. It is better to keep your BG “ups and downs” as stable as possible. This ensures that other systems in your body are not unduly “taxed” by the gyrations of a BG roller coaster.

Hope this helps. And good luck to you!


Everyone here has excellent explanations. The general medical guidelines say:
Aerobic will lower your BG, so lower your basal in advance/eat some carbs
Anaerobic will raise your BG, so you might not adjust basal or even need a bolus.
Mixed activity might raise or lower your BG.

You’ll have to track your insulin on board, carb intake, type of exercise, and exertion level until you can hone in on what works for you. And have access to simple sugar just in case diabetes throws you a curve ball and your BG drops unexpectedly.