There are usually two different classes of medication's used to decrease blood sugars. Artificial Insulin or just plainly Insulin, is the most direct, and can help maintain a low blood sugar in severely uncontrolled Type II diabetes, which does produce insulin, but it is insufficient or is not used properly. (which is usually controlled the medication and proper dietary and exercise). Additionally Insulin is the only medication that is used for Type I diabetics, as this diabetes involves the lack of production of insulin.
Type II diabetics are also usually given oral medication to help maintain a normal blood sugar. Metformin is a very common one, but others including Glipizide and Pioglitizone.