There are many causes of low blood sugar, and in the population can be divided into diabetic patients and non-diabetic patients, and the two groups of people appear for different reasons. The common reasons for diabetic patients are: 1. low blood sugar due to poor food intake and hunger, 2. inappropriate use of insulin, incorrect injection of insulin or incorrect dose of insulin, resulting in excessive injection of insulin, followed by low blood sugar. Or the amount of food is reduced but the insulin dose is not monitored, resulting in a drop in blood glucose. 3. Improper use of hypoglycemic drugs, especially the improper use of sulfonylureas is most likely to lead to hypoglycemia. 4. For type 1 diabetic patients, their own poor pancreatic function, prone to hypoglycemia. The common causes of low blood glucose in non-diabetic patients are: 1. after drinking a lot of alcohol, because alcohol can inhibit the output of liver glycogen, resulting in a drop in blood glucose. 2. islet cell tumor, due to the abnormal secretion of insulin from the tumor, followed by repeated hypoglycemia. 3. liver failure can lead to impaired glycogen storage and release in the liver and impaired glycemic mechanism and kidney failure can lead to impaired excretion of drugs and toxins, which can lead to low blood glucose. 4. 4. Impaired absorption of food due to major gastrectomy and the release of insulin-like substances due to other malignant tumors may also lead to low blood sugar. In summary, there are many causes of low blood sugar, and even unexplained low blood sugar.