Because of the damage caused by high blood glucose, it is important to treat diabetes mellitus. The goal is to maintain a normal blood glucose level. The normal range for blood glucose is 80-120 mg/dL (milligrams of glucose per deciliter of blood) or 3.5-7 mmol/l (millimole per liter of blood). These are different ways of saying the same thing, much like yards and meters are different units of distance measurement.