Diabetes mellitus is a metabolic disease. Diabetes mellitus is a group of metabolic diseases characterized by chronic hyperglycemia due to multiple etiologies and caused by defective insulin secretion and/or utilization. Diabetes mellitus is categorized on the basis of etiologic evidence as type 1 diabetes, type 2 diabetes, other specific types of diabetes, and gestational diabetes. Long-term carbohydrate, as well as fat and protein metabolism disorders can cause multi-system damage, leading to chronic progressive lesions, hypoplasia and failure of tissues and organs, such as the eyes, kidneys, nerves, heart, blood vessels, etc.; acute severe metabolic disorders, such as diabetic ketoacidosis (DKA) and hyperosmolar hyperglycemic syndrome, can occur in severe conditions or stress. Diabetes mellitus is a clinical syndrome caused by a combination of genetic and environmental factors, but its etiology and pathogenesis have not yet been fully elucidated. If diabetes is detected, it is necessary to go to a regular hospital as soon as possible.