Determining When to Check Your Blood Glucose

You need to know when you should monitor your blood sugar levels and what your glucose range should be. You and your health care team should determine this. It is generally recommended that you test your blood sugar just before you exercise, every 30 minutes during exercise, and 15 minutes after exercise. To prevent delayed-onset hypoglycemia, which typically occurs in the early stages of your exercise program or when the intensity of your activity increases, you should measure your glucose levels 6, 12, and 24 hours after cessation of exercise until your program has stabilized.

As a general guideline once your plan has stabilized, make sure that before exercising your glucose is at or slightly above 100 mg/dl. If your glucose is below 100 mg/dl, you should eat or drink something with carbohydrate in it until your blood glucose is in this range. The goal is to avoid hypoglycemia. If your glucose is at or above 100 mg/dl, then you need to take into account the effect that insulin or another glucose-lowering agent and exercise will have on your blood glucose, as discussed in detail in chapter 4. For instance, if you take insulin or have it in your system just before you exercise and you have not eaten, you are likely to experience a significant drop in your glucose level. Furthermore, it is generally accepted that exercise should be postponed if the glucose is more than 250 mg/dl and ketones are present in the urine, or if your glucose is greater than 300 mg/dl. (You can measure the urine ketone levels with urine test strips, which are available at your local pharmacy.) The American College of Sports Medicine (ACSM) guidelines state that if your glucose is between 200 and 400 mg/dl, you should consult your physician before exercising. If your glucose is greater than 400 mg/dl, the ACSM suggests that you do not exercise.