Why Does My Sugar Go Up After Exercise?

| Jun 1, 1994

Question: Why does my blood glucose (BG) sometimes rise after exercise?

Answer: If an inadequate amount of insulin is present in the blood allowing the BG to rise to about 250 to 300 mg/dl, then exercise may cause a further rise in BG rather than the expected drop. Low insulin coupled with physical activity stimulates the secretion of several other hormones such as epinephrine, norepinephrine, cortisol, glucagon, and growth hormone. Collectively these hormones trigger the liver to release glucose into the blood, thereby increasing the BG rather than decreasing it. The hormones also increase the breakdown of fat but limit the uptake of fat by muscle cells. The liver converts some of the fats to strong acids called ketones. The ketones may build up in the blood producing a state called ketoacidosis. This event is far more likely to occur in people with type I diabetes.

To prevent the problem the BG should be checked before exercise and if the level exceeds 250, then exercise should be delayed until it decreases well below 250. The urine should be checked for ketones and if they are present, exercise at this time will exacerbate the problem.

A second cause of the rise in BG during and after physical activity is highly vigorous exercise. The more intense exercise is, the greater the secretion of glucose from the liver. During the strenuous session, stress hormones will be secreted in large quantities which will then stimulate the liver to release glucose. This is an interesting paradox: the more vigorous the exercise the more glucose released by the liver with a likely rise in BG rather than a fall. To make matters worse, the level of stress hormones in the blood may be elevated for several hours after intense exercise causing the liver to continue the outpouring of sugar. Thus, the rise in BG may last for a number of hours once the exercise is completed. Additional BG monitoring may be needed until the values have stabilized.

Athletes who workout strenuously on a regular basis may not need to eat as large a feeding as expected before strenuous sessions. Also, as the body adapts to intense training, the hormonal secretion decreases when the same intensity workouts are done. Consequently, an intense workout at the beginning of a season that caused a surge in BG may cause a lesser rise in BG at mid-season.

In summary, monitor BG before exercise, during exercise if the sessions last beyond an hour, and after exercise one or more times. For non-athletes, high-intensity exercise isn't needed to improve fitness, health in general, and improve BG control. It even tends to make BG management more difficult and increase the risk of injury, sore muscles, and heart attack, and may discourage you from sticking with your exercise regimen.

Click Here To View Or Post Comments

Categories: Blood Glucose, Blood Sugar, Diabetes, Exercise, Fitness, Insulin

Take the Diabetes Health Pump Survey
See What's Inside
Read this FREE issue now
For healthcare professionals only

You can view the current or previous issues of Diabetes Health online, in their entirety, anytime you want.
Click Here To View

See if you qualify for our free healthcare professional magazines. Click here to start your application for Pre-Diabetes Health, Diabetes Health Pharmacist and Diabetes Health Professional.

Learn More About the Professional Subscription

Free Diabetes Health e-Newsletter

Top Rated
Print | Email | Share | Comments (9)

You May Also Be Interested In...


Posted by Anonymous on 15 September 2008

I am a type 2 and my bg never gets close to those levels (anymore), but I still have the elevation in BG after exercising. Very angering, makes me want to not exercise.

Posted by Anonymous on 4 June 2009

Measured my BG before a fast 4 mile walk. It was 84. Ate 7 peanut MM's before the walk. 20 minutes after the walk, which took about an hour, my BG was 148. Crazy. No immediate benefits, but dr. said "to keep it up. Exercise is good." We will see.

Posted by Anonymous on 20 May 2012

Yesterday i did some soccer playing and after 25-30 minutes we took a brake. while taking the break i started to feel realy unconfortable and dry mouth when talking with friends. I didn't know what was going on. My GC alwasy been 91 to 105 since i was diagnosed T2 a month ago. After the game i ck my glucose and i was 139 ,i was worry and did'nt know why. I started to do a google search and found the reason. I really appreciate sites like this, a piece of mind for newbies like me. I will keep exercising though, i am loosing weight and feeling much better.

Posted by Anonymous on 29 May 2012

I have had diabetes for many years. Through the years I've upped the intensity of my exercise, started with walking, jazzercise, now I'm doing boxing and sports conditioning. I'm noticing the rise in BG as well. As of right now, I'm going to keep on doing it. For once in my life I am getting fit! I believe the benefits outway the temporary spikes. I'll be seeing my doctor next week, so we'll see!

Posted by Anonymous on 28 August 2012

I just started taking an injection of Victoza to lower my A1c from 7.9 back to my average 6.0. I went to my routine exercise class with a BS of 117. During the exercise I seemed to get fatigued quicker than normal. Had dry mouth and blurred vision. Took by BS when I returned to my car and got a reading of 317. My highest to date was 189. I ate some protien and drank alot of fluids. 3 hours later my BS was down to 85. By then I felt totally wiped out rather than having that bust of energy I usually have after working out. Has anyone else experienced such a dramatic spike while working out on this med?

Posted by Anonymous on 3 October 2012

I have been working out pretty hard since June of this year. I noticed my BG going up during workouts. Been hitting the weights as well. I have dropped Glipizide due to crashing every time I take it, but now I am shooting insulin as well as taking 2K Metformin everyday. Hope I'm going in the right direction because I feel better than I have for several years.

Posted by Anonymous on 26 March 2013

Finally! An explanation that makes sense! Thank you.

I just spent 2-3 hours digging up cottoneaster roots, rested a half hour, then tested: 202 mg/dl. This knowledge will help be predict sugar levels.

Posted by Anonymous on 9 July 2014

I have started exercising and have noticed that BS levels are up after exercise. My BS this morning was 154 and after execise it went to 194. This has happened several times and it worrries me. I will mention this to my doctor when I see him next month. I appreciate the comments I have found at this site.

Posted by Anonymous on 14 July 2014

Pre diabetic for years gained 25lbs and now diabetic . Upon exercising found my BG was higher than without exercise . Not on meds yet . Appointment with specialist not for another 3 weeks . Managed to reduce BG from average of 11 to an average of 6.7 in 3 weeks . Not sure of measurements shown in the previous comments as in Canada this is what our BG indicators show . Is it possible to translate from measures shown in previous text to our measure . I find confusing . Would appreciate a chart to show comparisons of your scale of measures to ours . Thanks so much for information answer my questions on why BG was going up. Wondering if less strenuous exercise would reduce the effects of high BG ?

Add your comments about this article below. You can add comments as a registered user or anonymously. If you choose to post anonymously your comments will be sent to our moderator for approval before they appear on this page. If you choose to post as a registered user your comments will appear instantly.

When voicing your views via the comment feature, please respect the Diabetes Health community by refraining from comments that could be considered offensive to other people. Diabetes Health reserves the right to remove comments when necessary to maintain the cordial voice of the diabetes community.

For your privacy and protection, we ask that you do not include personal details such as address or telephone number in any comments posted.

Don't have your Diabetes Health Username? Register now and add your comments to all our content.

Have Your Say...

Username: Password:
©1991-2014 Diabetes Health | Home | Privacy | Press | Advertising | Help | Contact Us | Donate | Sitemap

Diabetes Health Medical Disclaimer

The information on this site is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment. All content, including text, graphics, images, and information, contained on or available through this website is for general information purposes only. Opinions expressed here are the opinions of writers, contributors, and commentators, and are not necessarily those of Diabetes Health. Never disregard professional medical advice or delay seeking medical treatment because of something you have read on or accessed through this website.