There are various dosage forms of insulin, and it is very important to be careful in the specific selection. Short-acting insulin is characterized by fast absorption and short duration, which can control blood sugar in a shorter period of time and facilitate dose adjustment. It is appropriate to choose in the following cases: 1) the initial treatment stage of insulin, which is convenient to figure out the dose; 2) the rescue of diabetic ketoacidosis and hyperosmolar coma; 3) stressful conditions such as serious infection and surgery; 4) the elimination of postprandial hyperglycemia; 5) the implementation of intensive treatment with medium- and long-acting insulin. Intermediate-acting insulin has an onset and duration of effect between short-acting and long-acting, and is mainly used to supplement insufficient basal insulin secretion. Combination therapy: 1) oral hypoglycemic drugs during daytime and injection of intermediate-acting insulin before bedtime; 2) replacement therapy: subcutaneous injection of intermediate-acting insulin before breakfast and dinner or injection of short-acting insulin before three meals and intermediate-acting insulin before bedtime. Long-acting insulin has a slow onset and a long duration of effect, and is mainly used to supplement basal insulin secretion deficiency and reduce nighttime or fasting blood glucose. It is usually not used alone, but often combined with short-acting insulin to implement intensive treatment. Note: Medium-acting insulin, long-acting insulin and short-acting insulin analogues cannot be used for intravenous injection, and cannot be used for the rescue of acute complications of diabetes (ketoacidosis coma).