Insulin is injected subcutaneously, and insulin is an important method of blood glucose control for people with diabetes. There are many types of insulin, which can be categorized into short-acting insulin, intermediate-acting insulin, long-acting insulin, as well as rapid-acting insulin analogs and long-acting insulin analogs, based on their duration of action. All insulins can be injected subcutaneously. The regimen of insulin injection therapy needs to be decided specifically under the supervision of a doctor, depending on the patient’s age, weight, blood sugar, and complications, and can be given subcutaneously once daily, twice daily, three times daily, or even four times daily. Subcutaneous injection of insulin therapy is mainly in the abdomen around the navel, upper arms, outer thighs and buttocks, of which the fastest absorption rate is when injected subcutaneously in the abdomen. In addition to subcutaneous injection, individual patients need intravenous insulin when diabetic ketoacidosis, hyperosmolar coma or inability to eat, the insulin that can be injected intravenously is short-acting insulin, also known as normal insulin, regular insulin, and so on.