Blood sugar meters or blood glucose monitors are commonly prescribed by doctors to patients with diabetes for tracking their blood sugar levels at home. The timing and manner of these tests will be explained to you by your doctor. Among the information, you can include in your notes is the time of day, the meal you just ate, your recent activities, your current medications, and other factors that may affect your reading. This is due to the fact that normal blood sugar levels for diabetic patients vary depending on the situation. In general, target levels for adults are 70-130 mg/dL before meals, less than 180 mg/dL after meals, 100 mg/dL before exercise (if taking insulin), and 100-140 mg/dL before sleeping.