For those taking insulin or insulin secretagogues, care should be taken to avoid hypoglycemia.

• Checking your blood glucose before, during and after exercise will provide a framework on which to base your regular routine of insulin, food, and exercise regimen. 
• If pre-exercise blood glucose levels are < 100mg/dL (5.6 mmol/L), some carbohydrate may need to be eaten.  About 15 grams of carbohydrate is usually enough to reduce the risk of hypoglycemia.

15 grams of carbohydrate is:

• A 2 inch in diameter apple
• 4 ounces of banana (about ½ a medium banana)
• About 17 medium grapes
• 1 cup of milk
• ½ cup of most juices
• 1 slice of bread
• 3 to 5 crackers

If pre-exercise blood glucose is high (>250 mg/dL), you should check your urine for ketones. If there are no ketones, you are probably fine to exercise. If there are ketones, you should not exercise.