Long-term injection of insulin can appear the following hazards: 1, hypoglycemic reaction: mainly manifested as insulin injection dose is too large, diet is not timely or diet is not enough; 2, hyperinsulinemia: obese patients with type 2 diabetes mellitus may appear hyperinsulinemia, and is often accompanied by insulin injections in large doses; 3, insulin edema: diabetes mellitus in the early stage of the blood glucose is controlled, the body is often in the lack of sodium, water and decrease of extracellular fluid. After the use of insulin, 4-6 days of blood glucose control will cause water and sodium retention, resulting in facial and limb edema, with insulin treatment, more patients can slowly absorb this edema; 4, insulin allergy: in the local mainly manifested as the injection of local skin itching and urticaria, the systemic allergic reaction is mainly manifested as systemic urticaria and allergic purpura. Insulin allergic reaction can appear in the initial use of insulin or patients use insulin 1 month later, can also appear in patients stop using insulin, when using insulin again; 5, long-term injection of insulin can produce insulin resistance, patients in the absence of diabetic ketoacidosis, if the daily dose of insulin is more than 200U, for 2 days, it is necessary to consider that there is insulin resistance.