Insulin is a hypoglycemic hormone secreted by pancreatic beta cells, and insulin is the only hypoglycemic hormone in the human body. The principles of insulin to lower blood sugar are as follows: First, insulin can promote glycogen synthesis, and after eating insulin will promote the conversion of blood sugar into glycogen reserves to avoid the rise of blood sugar, so insulin can effectively avoid high blood sugar after meals. Second, insulin can promote protein and fat synthesis, inhibit protein and fat decomposition, so that the reduction of gluconeogenic raw materials can further reduce blood sugar. Therefore, insulin is a pro-synthetic hormone that can promote the synthesis of protein, fat and glycogen and inhibit the breakdown of protein, fat and glycogen, playing an important role in maintaining the dynamic balance of blood glucose.