Oral hypoglycemic drugs are an important method of treating diabetes, and metformin is the most commonly used oral hypoglycemic drug in clinical practice. The mechanism of metformin for lowering blood sugar is as follows. I. Promote glucose uptake and utilization, and inhibit glucose production by the liver. Second, increase anaerobic enzymes, which can lead to increased lactate production. III. Improves insulin resistance and increases insulin sensitivity. IV. It can reduce body weight and help patients control their weight. Because metformin does not act through insulin, metformin alone does not cause severe hypoglycemia. The most important side effects of metformin are gastrointestinal irritation, affecting liver and kidney function, and the possibility of inducing lactic acidosis in patients with cardiopulmonary insufficiency. Metformin can be combined with other oral hypoglycemic drugs and also with insulin. Metformin is mainly used for type 2 diabetic patients, but also for type 1 diabetic patients over ten years old.