Diabetes mellitus is mainly divided into type 1 diabetes mellitus and type 2 diabetes mellitus, etc. The causes of different types of diabetes mellitus are different, mainly genetic, immune, dietary and other factors. 1. Type 1 diabetes: Type 1 diabetes is caused by the destruction of pancreatic β-cells, resulting in a lack of insulin, resulting in elevated blood glucose, mostly autoimmune diseases, mainly genetic factors, environmental factors, autoimmune factors involved in the onset of its environmental factors include viral infections, chemical toxins, diet and so on. 2. Type 2 diabetes mellitus: Type 2 diabetes mellitus is a chronic disease caused by relative insufficiency of insulin secretion or insulin resistance, resulting in increased blood glucose levels, caused by the joint action of genetic factors and environmental factors, environmental factors include aging, obesity, high-calorie diets, over-nutrition, and insufficient physical activity. 3. Special type of diabetes: such as gestational diabetes, due to abnormal hormone levels during pregnancy, the regulation of glucose metabolism is affected to a certain extent, and often after delivery, blood glucose can return to normal. It is recommended that patients seek timely medical examination, clear diabetes typing, targeted treatment, in life to develop good habits, while paying attention to monitoring blood glucose, regular review.