An antihyperglycemic drug. Metformin hydrochloride (Glucophage) is used to treat type 2 diabetes mellitus. Metformin hydrochloride is used to lower the blood sugar level and to make it possible for the body to convert blood sugar to energy, which it does by decreasing the production of glucose by the liver and increasing tissue responsiveness to insulin. Metformin may be used alone, with another oral hypoglycemic medicine called a sulfonylurea, or with insulin, to lower blood sugar. This medication is not effective for type 1 diabetes, which requires insulin injections.