Insulin is the only hypoglycemic hormone in the body, and is an effective method of controlling blood sugar in diabetic patients. Insulin is mainly used for type 1 diabetes, but also for type 2 diabetes that is ineffective with oral hypoglycemic drug treatment, combined with acute and chronic complications, and gestational diabetes. Insulin is a peptide hormone that requires special temperatures for its storage and transportation. Insulin must be used within the expiration date, once the use of expired insulin may occur the following hazards: First, the biological role of insulin is reduced or disappeared, when the role of insulin decreases, the patient subcutaneous injection of insulin can not play a corresponding hypoglycemic effect, which will lead to blood glucose elevation. Diabetic ketoacidosis may occur in patients with markedly elevated blood glucose, especially in patients with type 1 diabetes mellitus who have very poor pancreatic islet function. Second, insulin allergy, insulin is protein, expired insulin is more prone to protein denaturation, insulin allergy, severe cases may occur anaphylaxis. Third, aggravate the irritation symptoms of the injection site, when the injection of expired insulin may make the irritation symptoms of the injection site aggravated.