The common types of diabetes mellitus are type 1 diabetes mellitus, type 2 diabetes mellitus, etc. Different types of diabetes mellitus have different causes; the causes of type 1 and type 2 diabetes mellitus have not yet been fully clarified. Type 1 diabetes mellitus is considered to be related to factors such as heredity and autoimmunity; type 2 diabetes mellitus is considered to be related to factors such as heredity, environment, and insulin resistance. Type 1 diabetes mellitus: genetic susceptibility involves more than 50 genes, including HLA and non-HLA genes; environmental factors include viral infections such as mumps virus and rubella virus, as well as dietary and chemical toxins; and autoimmune factors include humoral immunity and cellular immunity, which all play an important role in the development of type 1 diabetes mellitus. 2. Type 2 diabetes mellitus: genetic predisposition, plus other factors such as aging and poor lifestyle; insulin resistance is predominant in the early stages, with progressive decline in pancreatic islet function occurring in the later stages. Patients with these factors and abnormal blood glucose or diabetes-related symptoms are advised to go to the hospital.