Patients with type 1 diabetes are absolutely deficient in insulin and require lifelong insulin therapy. If a type 2 diabetic patient’s blood glucose is still poorly controlled after dietary control, exercise therapy, and treatment with multiple oral hypoglycemic agents, insulin therapy needs to be added to the oral hypoglycemic agents. In type 2 diabetic patients with acute complications of diabetes, such as diabetic ketoacidosis or hyperosmolar hyperglycemic syndrome, treatment with insulin is also required. Insulin is also required when a diabetic patient undergoes a larger surgical procedure, before the procedure and until the patient resumes eating after the procedure. If pregnant and breastfeeding women with diabetes do not reach the blood glucose target through diet and exercise therapy, they can also only use insulin to lower their glucose. For newly diagnosed type 2 diabetic patients, short-term insulin therapy is also recommended if glycosylated hemoglobin is greater than 10%, suggesting poor islet function.