Diabetic patients can start treatment with insulin when they have type 1 diabetes, gestational diabetes, type 2 diabetes with ineffective oral hypoglycemic drugs, and diabetic ketoacidosis. 1. Type 1 diabetes mellitus: the insulin in the patient’s body is absolutely insufficient, and insulin therapy must be used for a long time to control blood sugar. 2. Gestational diabetes mellitus: oral hypoglycemic drugs should not be used, insulin can be used to control blood sugar. 3. type 2 diabetes mellitus: oral hypoglycemic drugs are not effective: oral hypoglycemic drugs are difficult to effectively make the blood glucose standard, insulin can be used to reduce the risk of acute and chronic complications of diabetes mellitus. 4. Acute complications: such as diabetic ketoacidosis, hyperosmolar non-ketotic diabetic coma, etc., at this time as soon as possible with insulin emergency treatment, to avoid delays. 5. Other: insulin treatment can be preferred for newly diagnosed but high blood glucose type 2 diabetes patients, especially those with severe weight loss. Common adverse reactions to insulin include hypoglycemia, mild edema, blurred vision, allergic reactions, and fatty atrophy or hyperplasia. Patients with diabetes need to follow their doctor’s instructions for medication.