A drug used to treat diabetes mellitus (a condition in which the body cannot control the level of sugar in the blood). It is also being studied in the treatment of cancer. Metformin hydrochloride decreases the amount of glucose (a type of sugar) released into the bloodstream from the liver and increases the body’s use of the glucose. It is a type of antidiabetic agent. Metformin is the active ingredient of metformin hydrochloride. Also called Glucophage.