Indications for insulin therapy. (1) Patients with type 1 diabetes mellitus; (2) Patients with type 2 diabetes mellitus who are taking more than two oral hypoglycemic drugs and whose glycosylated hemoglobin cannot reach the standard; (3) Women with gestational diabetes mellitus and diabetes mellitus combined with pregnancy; (4) Patients with diabetes mellitus complicated with acute infection, chronic severe infection, trauma, surgery and acute cardiovascular and cerebrovascular infarction; (5) Patients with diabetes mellitus combined with chronic hepatic and renal insufficiency of any cause; (6 (6) Patients with type 2 diabetes mellitus with significant wasting; (7) Patients with type 2 diabetes mellitus with hyperglycemia; (8) Some patients with other types of diabetes mellitus, especially those with tumors of pituitary origin, pancreatic disorders, and B-cell function defects. Types of insulin and methods of application. At present, the insulins commonly used in clinical practice are short-acting, medium-acting, long-acting, fast-acting and premixed, with many types of preparations and different characteristics and effects. The application methods are: (1) subcutaneous injection, including intermittent subcutaneous injection and continuous subcutaneous injection; (2) intravenous injection; (3) mucosal absorption; (4) intraperitoneal infusion. Type 2 diabetes insulin treatment modalities. (1) Short-term insulin therapy. The duration varies from a few hours to several weeks; almost every patient with type 2 diabetes, including those with pre-diabetes, may need short-term insulin therapy in case of infection, surgery, trauma or other stressful situations, and the mode of intravenous or intermittent subcutaneous insulin injection can be chosen according to the specific situation. (2) Long-term insulin therapy. It is mainly applied to type 2 diabetic patients with eventual B-cell failure, who cannot use oral hypoglycemic drugs due to chronic liver and kidney insufficiency or who have combined chronic comorbidities of diabetes and need strict glycemic control. Except for a few patients with severe pancreatic B-cell failure who can choose continuous subcutaneous insulin injection mode, intermittent subcutaneous insulin injection mode is generally used. (3) Staged insulin therapy. It is often used in patients with acute abnormal liver and kidney function, combined with chronic severe infection, those with excessive blood glucose in a short period of time, combined with pregnancy and type 2 diabetes who are too thin. The treatment can be changed to oral hypoglycemic drugs after the above conditions are relieved or remitted. The choice of insulin subcutaneous injection method. In the case of subcutaneous insulin injection therapy, the specific method should be selected according to the function of pancreatic B cells, the change of blood sugar within one day and the combination of oral medication. (1) Continuous subcutaneous injection (insulin pump). It is mainly used in type 1 diabetes and late type 2 diabetes with B-cell failure, and it is not necessary to combine oral hypoglycemic drugs. Only those who are overly obese or have a tendency to gain weight after treatment can combine with biguanides or glycosidase inhibitors. After treatment, it is still necessary to adjust the dosage in time on the basis of monitoring blood sugar to assist in good control of blood sugar. (2) Subcutaneous injection 4 times a day. Its indications are similar to those of continuous pump injection, mainly for patients with type 1 diabetes and type 2 diabetes with B-cell failure, but also for patients with acute complications or when strict blood glucose control is needed before special treatment such as surgery, by injecting one dose of short-acting insulin before three meals and medium-acting or long-acting insulin preparations before sleep. (3) Subcutaneous injection three times a day. It is suitable for type 2 diabetic patients whose B-cell function has not completely failed and who have a little basal secretion, other special types who need to be treated with insulin, type 2 diabetic patients with liver function impairment, or patients who have irregular lunch due to work. It is often one injection of short-acting insulin before breakfast and lunch, and a mixture of short-acting and medium (long) acting insulin (or premixed) before dinner. (4) Twice daily insulin injections. It is the most common injection method for type 2 diabetic patients, and even some type 1 diabetic patients also use this injection method, that is, one injection of short- and long- (medium-) acting mixed (or premixed) insulin before breakfast and dinner. The choice of dosage form and dose is mainly based on the usual monitoring of blood glucose levels. (5) One insulin injection per day. It is mainly used for those whose fasting blood glucose is not normal when treated with oral hypoglycemic drugs, or those whose blood glucose control is poor for only one period of time, and it is difficult to adjust with oral drugs. If only fasting blood sugar is not up to standard, one injection of long-acting or medium-acting insulin can be given in the morning or before going to bed at night; or for those whose blood sugar level is not up to standard before and after Chinese meal, one injection of short- and long- (medium-) acting mixed (or premixed) insulin can be given before breakfast. In the above cases, oral hypoglycemic drugs are taken in the same way as before. Insulin injection dose selection. The principle is to gradually increase the dosage from a small amount, starting from 4U for a single dose and 0.3-0.5U/Kg of body weight for the whole day, and allocate it to the dosage in each injection (the following table). Number of insulin injections per day Before breakfast Before lunch Before dinner Before bedtime 4 injections per day 2/5 1/5 1/5 1/5 1/5 3 injections per day 2/5 1/5 2/5 3 injections per day 3/5 1/5 1/5 2 injections per day 3/5 2/5 Insulin injection site selection. The subcutaneous areas for insulin injection are mainly the lateral forearm, abdominal wall and anterolateral femur. Due to the difference in local blood circulation, generally after subcutaneous injection in the middle and lateral forearm and abdominal wall, it is absorbed about twice as fast as that in the lateral anterior femur. When injecting insulin, the injection site can be chosen according to different needs. Generally, subcutaneous injection of the abdominal wall with fast absorption in the morning is more conducive to postprandial blood glucose control, while the femoral region is chosen before going to bed at night to facilitate the maintenance of insulin action.