The etiology and pathogenesis of type 2 diabetes mellitus are complex and have not been fully elucidated. At present, it is mainly believed to be related to genetic factors and environmental factors. 1. Etiology: Genetic factors: the homozygosity rate of type 2 diabetes mellitus in identical twins is close to 100%. Environmental factors: aging, poor living habits, low physical activity, over-nutrition, stress and other factors may be related to diabetes. 2. Pathogenesis: Defective β-cell function leads to varying degrees of tissue insulin resistance as well as insulin deficiency in the body, which is an important part of causing type 2 diabetes. For patients with type 2 diabetes mellitus, they should consult a doctor in time and follow the doctor’s instructions for standardized treatment.