Insulin is the only hormone that exists in the human body that can lower sugar. It is suitable for patients with type I diabetes, patients with type 2 diabetes who cannot reach the target with oral hypoglycemic drugs, patients who have contraindications to oral drugs, patients who have acute complications, pregnancy or severe liver and kidney insufficiency. Wang Yanyan, Department of Endocrinology, Shanghai Yueyang Hospital Insulin can be divided into animal insulin, human insulin and human insulin analogues. It can be divided into rapid-acting insulin, short-acting insulin, medium-acting insulin, long-acting insulin, and super-long-acting insulin according to the duration of action. Insulin injection sites include the upper and outer arms, abdomen, above the waist and back, buttocks and front and outer thighs, and should be injected in the subcutaneous tissue layer, not in the muscle layer, which is absorbed quickly and easily causes blood sugar fluctuations. The absorption rate varies in different parts of the body, with the abdomen, upper arms, thighs and buttocks slowing down in that order. Insulin should avoid high temperature and sunlight. Unopened insulin should be kept at 2~8 degrees, and opened insulin can be used for 1 month at room temperature. Insulin is not addictive, and the need for insulin is determined by the condition.