Subcutaneous insulin injections are one of the effective means of treating diabetes, but not all people with diabetes need insulin injections. The following conditions require insulin injections: I. Type I diabetes, also known as insulin-dependent diabetes, is mostly seen in children and adolescents. Type II diabetes can be treated with insulin when diet, exercise and oral medication are not effective. Type II diabetes combined with acute and chronic complications, such as ketoacidosis, lactic acidosis and hyperosmolar coma can be treated with insulin. IV. Diabetes combined with serious infections, heart attack, brain infarction and other serious diseases need insulin therapy. V. Patients in the perioperative period need insulin therapy. When diabetic patients undergo surgery, insulin therapy should be replaced in time before, during and after surgery. VI. Gestational diabetes and diabetes combined with pregnancy require insulin therapy. VII. Young diabetic patients who are clinically difficult to be typed and are wasting can be activated early for insulin therapy when their blood sugar is high.