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From America On-Line:

Can exercise cause high blood sugar if there is little to no insulin in the body? For example, I am a runner and usually run every day after school. Sometimes after I am finished, my blood sugar is high {over 200 mg/dL}, while others it is normal {around 100mg/dL}. Also, I can usually eat a snack before I run and have a normal blood sugar, but other times, even if I don't snack, I have normal blood sugars, and even occasional highs. Can you try to explain this to me, or offer some advise on how to regulate or know just exactly what I should do?


Blood glucose can become elevated after exercise as a result of insulin deficiency. Insulin deficiency also results in an excess of counterregulatory "stress" hormones (glucagon, epinephrine, cortisol, and growth hormone). This combination of not enough insulin and too much of the "stress" hormones causes the liver to produce two to three times more glucose than normal, leading to higher blood glucose levels.

Blood glucose levels can also increase during exercise if they are already high, because high intensity exercise (e.g., pacing yourself at a faster pace than usual) can stimulate your liver to break down stores of glycogen to create glucose. You might discover by testing your post exercise blood glucose level is higher than when you started. If you have enough insulin available, your blood glucose will recovery rapidly. But if your levels of insulin are low, you could start producing ketones.

You did not mention if you test your blood glucose before exercise. Always check your blood glucose before exercise. If your blood glucose is less than or equal to 100 mg/dl, eat a snack then test your blood glucose in 20 to 30 minutes. If your blood glucose is over 100 mg/dl to 250mg/dl, go ahead an exercise. If your blood glucose is over 250 mg/dl, check for ketones. If you test negative for ketones, go ahead and exercise. If you test positive for ketones, do not exercise. You may not have enough insulin in your body. If you exercise in this situation you can drive your blood glucose level even higher. If your blood glucose is over 300 mg/dl, whether ketones are present or not, do not exercise.


Original posting 8 Apr 1998
Posted to Exercise and Sports and Hyperglycemia and DKA


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