The occurrence of diabetes is related to the absolute or relative insufficiency of the secretion function of pancreatic beta cells in the human pancreas. Insulin is one of the effective drugs for the treatment of diabetes mellitus. The suitable targets for insulin use in diabetic patients are: (1) type 1 diabetic patients; (2) newly diagnosed type 2 diabetic patients with initial onset; (3) type 2 diabetic patients who cannot control blood sugar well by diet control and oral hypoglycemic therapy; (4) diabetic ketoacidosis, diabetic hyperosmolar coma and lactic acidosis; (5) pregnancy and childbirth; (6) surgery, trauma, myocardial infarction, cerebrovascular accident, severe infection, etc. (6) Surgery, trauma, myocardial infarction, cerebrovascular accident, severe infection, etc.; (7) Combined with severe liver and kidney function impairment, etc. Some patients may have the misconception of “insulin addiction”. In fact, exogenous insulin only supplements the deficiency of endogenous insulin, so there is no problem of addiction. Insulin is classified by species: animal insulin, genetically recombinant human insulin, and insulin analogues. Classification by duration of action: fast-acting insulin analogues, short-acting insulin, intermediate-acting insulin, long-acting insulin (including long-acting insulin analogues), premixed insulin (including premixed insulin analogues). Classification by action characteristics: Mealtime insulin (after the first meal) – fast-acting insulin analogues, such as Novalax, Utro; short-acting human insulin, such as Novalax R, Utrolin R, Ganserin R. Basal insulin – long-acting insulin analogues, such as Novalax, Lexapro; medium-acting human insulin, such as Novalax N, Utrolin N. Premixed insulin: premixed insulin analogues, such as Novalax 30, Utrolin 25; premixed human insulin analogues, such as Novalax 30 , Eugenol 25; premixed human insulins, such as Novolin 30R/50R, Eugenol N70/30, Gansulin 30R. Doctors will use the appropriate insulin according to the specific situation of each diabetic patient in order to control blood sugar effectively and smoothly up to the standard. The available injection sites for insulin are: the lateral side of both upper arms (i.e. at the deltoid muscle), the front or front lateral side of both thighs, around the abdominal wall around the umbilicus (must be 5cm away from the belly button), etc. When injecting insulin, the skin can be pinched up to ensure subcutaneous injection, and stay at the injection site for 5-10 seconds after the injection is completed so that the drug can be fully absorbed and avoid extravasation of the drug. Insulin injection should be frequently changed at the injection site, and each injection site should be more than 2 cm apart from each other. When insulin is not in use, it should be kept in a refrigerator refrigerated at 2-8℃ to avoid decomposition and failure of insulin in a high temperature environment, while insulin should not be frozen and insulin needs to be applied within the expiration date.