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From Indiana, USA:

Can high blood sugars cause nausea during aerobic exercise? If not, what could be the cause? Also, why does my blood sugar sometimes go up after exercise instead of down? I am a 47 year old female with Type 2 and was diagnosed about three years and am controlling it with only diet and exercise at the present time.


Hyperglycemia (high blood sugars) can cause nausea, extreme thirst, frequent urination, dry skin, hunger, blurred vision and drowsiness. If your fasting blood glucose is over 300 mg/dl, your diabetes is in poor control and you need to check with your health care professional to make sure if it is okay for you to exercise.

Blood glucose levels can increase during exercise if they are already high for the following reason. High intensity exercise (e.g., walking faster than usual or pedaling up a steep hill) can stimulate your liver to break down stores of glycogen to create glucose. You might discover by testing your blood glucose after exercise that your blood glucose is even higher then when you started.

Regular exercise will, over time, help your body become better at using the insulin it produces. You have Type 2 diabetes which means your body is not properly using the insulin that it produces or it is not producing enough insulin to meet its needs. Insulin plays an important role in allowing glucose to enter the cells in your body so it can be used for energy. Exercise can help make you body more receptive to insulin. As your tissues become more sensitive to the insulin your body makes, more glucose can move into the cells, thus reducing the amount glucose left circulating in the blood.

Remember: Always check your blood glucose before and after exercise. If it is your first time engaging in an activity/exercise (e.g., swimming laps, riding a bike) that will last for more than 30 minutes, check your blood glucose 30 minutes into the activity. This will give you an indication as to how your body is reacting to that particular activity/exercise.

General Guidelines for Physical Activity/Exercise

  • If your blood glucose is less than or equal to 100 mg/dl before exercise, eat a snack.

  • If your blood glucose is greater than 100 mg/dl and not greater than 250 mg/dl before exercise, go ahead and exercise.

  • If your blood glucose is greater than 250 mg/dl before exercise, check for ketones. If ketones are present, do not exercise. Exercise will worsen your control.

  • If blood glucose is greater than 300 mg/dl before exercise, do not exercise whether you have ketones or not. Exercise will worsen your control.


Original posting 14 Nov 1998
Posted to Exercise and Sports and Hyperglycemia and DKA


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