If you take insulin or oral pills that lower your blood glucose, be sure to check your blood glucose level before you exercise. If your blood glucose is less than 100 mg/dl, eat or drink something containing 15 grams of carbohydrate to raise your blood glucose to a safe range before exercising. Anticipate the need to consume at least 15 grams of carbohydrate for each 20–30 minutes of moderate-intensity activity to avoid hypoglycemia (low blood glucose) during exercise.
When you first start an exercise program, check your blood glucose before and after the activity to see what effect exercise has on your blood glucose level and to determine whether a change in your usual food intake or medication is needed. Be particularly careful if you exercise during the peak action time of your insulin. (The peak action time is when insulin lowers blood glucose the most, and it differs from one type of insulin to the next. Check the literature that comes with your insulin for information on how quickly it starts working and when it reaches its peak action.) Exercising around the same time each day may have a more predictable effect on your blood glucose than exercising at different times, but there may still be instances when your blood glucose does not respond the way you expect it to.
Avoid exercise if your blood glucose level is higher than 250 mg/dl and you have ketones in your blood or urine. Use caution if your blood glucose level is 300 mg/dl or higher and you have no ketones. A blood glucose level over 250 mg/dl means there may be a lack of available insulin in your system, which in turn means that some of the glucose in your bloodstream may not be available to be used as fuel by your muscles. In addition, exercising when your blood glucose level is this high can cause it to go even higher.
If you start exercising with a high blood glucose level, stop 15 minutes into the activity and check your level again. If it has gone up further, stop exercising and continue to check your blood glucose periodically for the next 90 minutes. If it has gone down from your pre-exercise level, it’s safe to continue exercising. Remember to watch for signs of hypoglycemia, as usual.
People with Type 2 diabetes who control their diabetes with diet and exercise are less likely to develop hypoglycemia during exercise or to experience large swings in blood glucose levels as a result of exercise. In fact, for these people, exercise has a predictable lowering effect on blood glucose level and is an important part of diabetes treatment.
Before you start any exercise program, you need a good pair of shoes that provide support and cushioning. For most activities, you’ll need some type of sneaker or walking shoe; for water aerobics or swimming, wearing water shoes is recommended to reduce the risk of injury. It’s important that the shoes you buy have adequate arch support and fit in both the heel and toe areas. Your heel should not be able to lift more than half an inch, and you should have wiggle room for your toes. These precautions are especially important for people with peripheral neuropathy who have lost feeling or sensation in their feet. Wearing socks is also important for foot protection.
The best time to purchase shoes is in the afternoon, when your feet are swollen and at their largest. To ensure you have a good fit, look for the shape of the shoe to match the shape of your foot. Make sure that you have at least one thumb’s width of space between your longest toe and the end of the shoe, and make sure the arch in the shoe matches the arch in your foot.