Avoid hypoglycemia. Assuming you have diabetes, the issue is probably how to avoid hypoglycemia. Plan to exercise after a meal; you may want to check your blood sugar prior/after exercise. Decrease Insulin (if on it) with anticipation of a low with your doctor's help. Consider changing the time of day that you exercise and make sure you have enough protein in your diet to help avoid lows hours following exercise.
Eat carbs. Eating carbohydrates should increase blood sugar before exercising.