If you have diabetes, exercise is one of the best things you can do for your health. It can improve your sensitivity to insulin and help you build muscle and shed excess fat, all of which go a long way to keeping this condition under control. However, you'll likely need to take a few more precautions when exercising than someone who doesn't have diabetes.
First, consult your doctor before starting or changing a fitness routine. This is especially important if you are overweight or have a history of heart disease, peripheral vascular disease, or diabetic neuropathy. For people who are 35 or older and who have had diabetes for more than 10 years, current guidelines recommend having a complete physical exam before beginning a new exercise program. Although not performed routinely, you may also have an exercise tolerance test (also known as a treadmill test) to monitor the performance of your heart and your blood pressure during exercise. The results can help you and your doctor determine the intensity of exercise that's best for you.
In general, the best time to exercise is one to three hours after eating, when your blood sugar level is likely to be higher. If you use insulin, it's important to test your blood sugar before exercising. If the level before exercise is below 100 mg/dL, eating a piece of fruit or having a small snack will boost it and help you avoid hypoglycemia. Testing again 30 minutes later will show whether your blood sugar level is stable.
Experts also caution against exercising if your blood sugar is too high (for example, over 250 mg/dL), because exercise can sometimes raise blood sugar even higher.
Because of the dangers associated with diabetes, always wear a medical alert bracelet indicating that you have diabetes and whether you take insulin. Also, keep hard candy or glucose tablets with you while exercising in case your blood sugar drops precipitously.
For more on how to live well after you've been diagnosed with diabetes, buy Diabetes: A plan for healthy living, a Special Health Report from Harvard Medical School.