Insulin is the only hypoglycemic hormone in the body and is an effective way to control blood glucose in diabetic patients. Insulin is mainly used for type 1 diabetes, but also for type 2 diabetes that is not treated with oral hypoglycemic drugs, combined with acute and chronic complications, and gestational diabetes. Insulin is a peptide hormone, and its preservation and transportation require special temperature. Insulin must be used within the expiration date. Once the expired insulin is used, the following hazards may occur: i. The biological effect of insulin is reduced or disappears. When the effect of insulin decreases, the patient cannot play the corresponding hypoglycemic effect after subcutaneous injection of insulin, which will lead to an increase in blood glucose. Diabetic ketoacidosis may occur in patients with markedly elevated blood glucose, especially in type 1 diabetic patients with very poor pancreatic islet function. Second, insulin allergy, insulin is protein, expired insulin is more likely to occur protein denaturation, insulin allergy, serious cases may occur anaphylaxis. Third, aggravate the irritation of the injection site, when the injection of expired insulin may aggravate the irritation of the injection site.