Normal blood sugar levels are less than 100 milligrams of glucose per deciliter during a fasting blood sugar test. Before a meal, blood sugar numbers should range between 70 and 130, and one to two hours after a meal, they should be less than 180, according to WebMD.
At bedtime, normal blood sugar levels range between 100 and 140. A diabetic should not exercise unless blood sugar levels are at least 100, WebMD notes. Diabetics should regularly track their blood sugar results, noting any medications taken, food eaten and exercise performed. As people age, the normal blood sugar levels increase slightly.