Can I Exercise With a High BG?
I've read that it's not good to exercise with a blood glucose of 250 or higher. Do you still burn calories when you are this high? Sometimes after exercise I'll test and my blood glucose has gone up, and I wonder if my workout was all for nothing. Asha Agar Brown, Minneapolis, Minnesota
Christy Parkin, MSN, RN, CDE, responds: Exercise is an important part of any diabetes treatment plan, and it's a powerful weapon against high blood glucose levels. However, diabetes and exercise pose special challenges, and for many people with diabetes, it's important that you test before and after exercise to prevent potentially dangerous blood glucose fluctuations.
The reason you need to be cautious with a blood glucose of 250 or higher is that there may not be enough insulin available to lower the blood glucose. This is especially important in type 1 diabetes, in which the body is insulin deficient and prone to ketones in the absence of insulin. During exercise, the muscles need more energy, so the body responds by releasing glucose into the bloodstream. This is why you can see your blood glucose rise after exercise. If the body does not have enough insulin to use the glucose, the sugar remains in the bloodstream, and this can cause more frequent urination that can lead to dehydration, especially when you lose more water from sweating and breathing hard during exercise. Additionally, if the body is forced to burn fat for fuel, as is the case when insulin levels are too low, toxic ketones can build up in the blood, and that can lead to diabetic ketoacidosis, a life-threatening condition.
To be safe, it is best to check your ketones when your blood glucose is over 250. This will indicate whether you have enough insulin on board to safely exercise. If ketones are present, hold off exercising until your blood glucose has come down. If there are no ketones present (in both type 1 and type 2 diabetes), then proceed cautiously with your exercise program.