Diabetes mellitus can be mainly categorized into type 1 and type 2 diabetes mellitus, as well as special types of diabetes mellitus and gestational diabetes mellitus, and the causes of different types of diabetes mellitus are somewhat different. For example, the causes of type 1 and type 2 diabetes have not been fully clarified, type 1 is mostly related to immunity, and type 2 is mostly considered to be genetic and environmental factors. 1. Type 1 diabetes: destruction of pancreatic β-cells, resulting in absolute lack of insulin. It is mainly related to autoimmunity, and is commonly positive for GAD and/or islet cell antibodies; the other is idiopathic, with no evidence of autoimmunity for unknown reasons. 2. Type 2 diabetes mellitus: the etiology of the disease has not been fully clarified, and it is considered to be related to genetic factors, with those who are genetically susceptible being more likely to develop the disease; environmental factors, such as aging, irregular lifestyle, over-nutrition, etc.; insulin resistance and pancreatic β-cell dysfunction; and abnormally elevated glucagon, and other factors mentioned above. 3. Gestational diabetes mellitus: mainly due to the increased demand for glucose by pregnant women after pregnancy, insulin resistance factors increase but insulin secretion is relatively insufficient. 4. Special type of diabetes mellitus: It is mainly caused by hereditary defects of pancreatic β-cell function, endocrine diseases, hereditary defects of insulin action, pancreatic exocrine diseases, drugs or chemicals, infections, rare immune-mediated diabetes mellitus, diabetes mellitus-related hereditary syndromes, etc. The presence of the above factors and the occurrence of blood glucose value are mainly related to the above factors. In the presence of these factors and abnormal blood glucose values, it is recommended to visit a hospital and ask your doctor to make a judgment.