Insulin can be injected in the leg, and the injection site of insulin in the leg is the outer thigh. Insulin therapy is an effective way to control blood glucose in diabetic patients. It is necessary to choose an appropriate insulin treatment plan under the guidance of a doctor according to the patient’s age, blood glucose, type of diabetes and complications. Insulin therapy can be administered once a day, twice a day, three times a day or four times a day. Commonly used insulin injection sites include the abdominal wall, upper arm, outer thighs and buttocks, with the abdominal wall having the fastest absorption rate, followed by the upper arm, and the buttocks and outer thighs having the slowest absorption rate. Therefore, insulins that require rapid onset of action, such as rapid-acting insulins and short-acting insulins, should be injected subcutaneously in the abdominal wall whenever possible. For medium-acting insulins or long-acting insulins, they can be injected subcutaneously in the buttocks or outer thighs. Patients with diabetes need to master the correct method of insulin injection and accurately draw the dose of insulin. Pay attention to the sterilization of the injection site and change the insulin injection site to avoid repeated injections.