Insulin is a protein hormone secreted by pancreatic beta cells, consisting of two peptide chains, A and B, with a total of 51 amino acids. It is not only the only hormone that can lower blood sugar in the body, but also an important hormone that promotes anabolism in the body. Insulin mainly acts on the liver, muscle and adipose tissue, and plays an important role in regulating the metabolism of energy substances such as sugar, fat and protein in the body. Under normal circumstances, the body can secrete insulin as needed according to the level of blood glucose to control blood glucose in the normal range. Once the amount of insulin secretion is insufficient or the body’s sensitivity to insulin decreases, various metabolic disorders will occur in the body, and glucose cannot be well utilized, resulting in diabetes. At this time, it is necessary to inject exogenous insulin subcutaneously to replace the insufficient secretion of own insulin. Tian Yong, Department of Endocrinology, Zhengzhou People’s Hospital