I. Overview Insulin therapy is an important tool to control hyperglycemia. type 1 diabetic patients need to rely on insulin to maintain life and must also use insulin to control hyperglycemia and reduce the risk of diabetic complications. type 2 diabetic patients do not need insulin to maintain life, but still need to use insulin to control hyperglycemia due to the failure of oral hypoglycemic drugs or the existence of contraindications to the use of oral drugs in order to eliminate the hyperglycemic symptoms of diabetes and reduce the risk of diabetic complications. At some point, especially when the disease is prolonged, insulin therapy may be the primary, or even necessary, measure for glycemic control. Medical professionals and patients must recognize that insulin therapy involves more components than oral medication, such as medication selection, treatment regimen, injection devices, injection techniques, self-monitoring of blood glucose, and actions taken based on blood glucose monitoring results. Insulin therapy requires more cooperation between medical personnel and patients than oral drug therapy. After starting insulin therapy, patients should continue to be instructed to adhere to diet control and exercise, and education and guidance should be strengthened to encourage and instruct patients to perform self-monitoring of blood glucose and acquire the skills to adjust the dose of insulin appropriately according to the results of blood glucose monitoring in order to control hyperglycemia and prevent the occurrence of hypoglycemia. All patients starting insulin therapy should be educated about the risk factors for the occurrence of hypoglycemia, symptoms, and self-help measures. Depending on the source and chemical structure, insulins can be classified as animal insulins, human insulins and insulin analogues. According to the difference of their action characteristics, insulins can be further divided into ultra-short-acting insulin analogues, regular (short-acting) insulins, medium-acting insulins, long-acting insulins (including long-acting insulin analogues) and premixed insulins (including premixed insulin analogues). Clinical trials have demonstrated that insulin analogs have similar ability to control blood glucose compared with human insulin, but insulin analogs are superior to human insulin in simulating physiological insulin secretion and reducing the risk of hypoglycemia (see Appendix 2 for details). II. Considerations for the initiation of insulin therapy Patients with type 1 diabetes require insulin therapy at the onset and lifelong insulin replacement therapy is required Patients with type 2 diabetes can start the combination of oral medication and insulin therapy if their blood glucose still does not reach the control goal based on the combination of lifestyle and oral hypoglycemic agents. Generally, when HbA1c is still greater than 7.0% after a larger dose of multiple oral medication combination therapy, insulin therapy can be considered to be initiated. Insulin should be used as the first-line treatment for diabetic patients with new onset and wasting that is difficult to identify with type 1 diabetes. Insulin therapy should be used as early as possible in the course of diabetes [including patients with newly diagnosed type 2 diabetes] when significant weight loss occurs without an obvious cause. Depending on the patient’s specific situation, basal insulin or premixed insulin can be used to start insulin therapy. 1. The use of basal insulin in the initiation of insulin therapy (1) Basal insulin includes medium-acting human insulin and long-acting insulin analogues. When only basal insulin is used for treatment, it is not necessary to stop using insulin pro-secretors. (2) Usage: Continue oral hypoglycemic drug therapy in combination with intermediate-acting or long-acting insulin analogues injected at bedtime. The starting dose is 0.2 U/per kg body weight/per day. Adjust the insulin dosage according to the patient’s fasting blood glucose level, usually every 3-5 days, and adjust 1-4 U each time according to the level of blood glucose until the fasting blood glucose standard is reached. (3) If fasting blood glucose control is ideal after 3 months but HbA1c does not reach the standard, adjustment of insulin treatment plan should be considered. 2. Use of premixed insulin (1) Premixed insulin includes premixed human insulin and premixed insulin analogues: depending on the patient’s blood glucose level, a 1 to 2 times daily injection regimen can be chosen. When using the 2-times-daily injection regimen, insulin stimulants should be discontinued. (2) Once-daily premixed insulin: The starting insulin dose is usually 0.2 U per kilogram of body weight per day, injected before dinner. The insulin dosage is adjusted according to the patient’s fasting glucose level, usually once every 3-5 days, and 1-4 U is adjusted each time according to the level of blood glucose until the fasting glucose standard is reached. (3) Pre-mixed insulin twice daily: The starting insulin dose is usually 0.2 to 0.4 U per kg body weight per day, distributed in a 1:1 ratio before breakfast and before dinner. The insulin dosage before breakfast and dinner is adjusted according to fasting blood glucose and pre-dinner blood glucose, respectively, every 3 to 5 days, and the dosage is 1 to 4 U per adjustment according to blood glucose level until the blood glucose standard is reached. (4) Premixed insulin can be used for a short period of time for 2 to 3 injections/d during the honeymoon phase of type 1 diabetes. Premixed insulin should not be used for long-term glycemic control of type 1 diabetes. III. Intensive treatment of insulin 1. Multiple subcutaneous insulin injections On the basis of the above insulin initiation therapy, after sufficient dose adjustment, if the patient’s blood glucose level still does not reach the standard or recurrent hypoglycemia occurs, the treatment plan needs to be further optimized. Intensive insulin therapy can be performed with mealtime + basal insulin or premixed insulin analogues three times a day. The usage is as follows: (1) Mealtime + basal insulin: Adjust the insulin dosage before bedtime and three meals according to the blood glucose level before bedtime and three meals, respectively, and adjust the dosage once every 3-5 days, and the dosage is 1-4 U each time according to the blood glucose level until the blood glucose reaches the standard. When starting a mealtime + basal insulin regimen, a regimen of adding mealtime insulin to basal insulin only before 1 meal (such as the main meal) can be used. After that, it is decided whether to add mealtime insulin before other meals according to the glycemic control. (2) Premixed insulin analogues 3 times a day: Insulin dose adjustment is made according to the blood glucose level before bedtime and 3 meals, and adjusted every 3 to 5 days until the blood glucose standard is reached. 2. Continuous subcutaneous insulin infusion (CS II) (insulin pump) is a form of intensive insulin therapy that requires the use of an insulin pump to implement treatment. The pharmacokinetic characteristics of insulin administered via CS II in vivo are closer to the physiological insulin secretion pattern. Compared to intensive insulin therapy with multiple subcutaneous insulin injections, CS II therapy is associated with a reduced risk of hypoglycemia. Only short-acting insulins or rapid-acting insulin analogues can be used in insulin pumps. The main groups for CS II are: patients with type 1 diabetes: women with diabetes who are planning to conceive and are pregnant or patients with gestational diabetes who need insulin therapy; and patients with type 2 diabetes who need intensive insulin therapy. IV. Application of insulin in special cases Hyperglycemia in patients with initial diabetes: For patients with initial type 2 diabetes with high blood glucose, it is difficult for oral drugs to achieve satisfactory control of blood glucose and improve the symptoms of hyperglycemia in a short period of time. Clinical trials have shown that treatment with insulin in patients with initial type 2 diabetes mellitus with high blood glucose levels can significantly improve insulin resistance and decreased β-cell function caused by hyperglycemia. Therefore, newly diagnosed type 2 diabetes mellitus with significant hyperglycemia can be treated with insulin for a short period of time, and after the hyperglycemia is controlled and the symptoms are relieved, the treatment plan can be adjusted according to the condition, such as switching to oral medication or medical nutrition therapy and exercise therapy. Attention should be paid to strengthening the monitoring of blood glucose, adjusting the insulin dose in a timely manner, and paying attention to avoiding the occurrence of hypoglycemia as much as possible. V. Insulin injection device and injection technique Patients can choose insulin injection devicez insulin injection pen, (insulin pen or special filling device), insulin syringe or insulin pump according to their personal needs and economic status. Proper selection of insulin injection device and proper insulin injection technique is an important part to ensure the effectiveness of insulin therapy. Patients receiving insulin therapy should receive education related to insulin injection techniques in order to master proper insulin injection techniques.