Diabetes mellitus (DM) is a condition that makes it hard for the body to control the level of glucose in the blood. Glucose is the main form of sugar that the body uses for fuel. Insulin, made by the pancreas, is a hormone that helps the body control the level of glucose in the blood. When glucose builds up in the blood, the result is a blood glucose level, called hyperglycemia. There are a number of ways to lower the blood glucose level. These include a correct diet for diabetes, medicine, and exercise. Exercise is a natural way a person with diabetes can help control his or her blood glucose levels. Muscles use more glucose during exercise.