Diabetes mellitus is a group of clinical syndromes caused by the interaction of genetic and environmental factors. It is caused by absolute or relative insufficiency of insulin secretion and decreased sensitivity of target tissue cells to insulin, resulting in disorders of sugar, protein, fat, water and electrolyte metabolism, with hyperglycemia as a common clinical feature, which can cause damage to multiple systems over time. Acute metabolic complications such as ketoacidosis can be caused under infection or stress. The occurrence of chronic complications such as coronary heart disease, ischemic or hemorrhagic cerebrovascular disease, blindness, and end-stage nephropathy in the diabetic population has become an important problem that seriously threatens people’s health. The prevalence of diabetes is now 2-4% and is significantly associated with genetics, age, obesity, and lifestyle changes. (1) Clinical manifestations: Type 1 diabetes, type 2 diabetes, gestational diabetes, and other special types of diabetes. Type 1 diabetes: can occur at any age, but mostly develops in young and old. Symptoms include polyphagia, polyuria, polydipsia, weight loss, and a tendency to ketoacidosis, which needs to be treated with insulin. There is a high rate of positive islet cell autoantibodies in the blood at the beginning of the disease. Type 2 diabetes can also occur at any age, but it mostly develops after the age of 40. Most patients have a slow onset, relatively mild clinical symptoms, and no tendency to ketoacidosis, but ketoacidosis or hyperosmolar coma can occur under severe illness or stress conditions. Diet, exercise and oral hypoglycemic drugs are effective, but as the disease progresses, progressive failure of pancreatic islet b-cell function or with acute and chronic complications also require insulin therapy. Gestational diabetes mellitus is a condition in which hyperglycemia or abnormal glucose tolerance is detected during pregnancy, but known diabetes mellitus combined with pregnancy does not fall into this category. Other special types of diabetes include those caused by pancreatic disease, endocrine disease (acromegaly, cortisolism, pheochromocytoma), drugs or chemicals, insulin or receptor abnormalities. Abnormal glucose tolerance is defined as fasting blood glucose that is not at the level of diagnosed diabetes, but is between normal and diabetic on an oral glucose tolerance test. These patients cannot yet be diagnosed with diabetes. (ii) Laboratory tests: Positive urine glucose is an important clue to the diagnosis of diabetes mellitus. Elevated blood glucose is the main basis for the diagnosis of diabetes. Fasting blood glucose ≥ 7.0 mmol/L and random blood glucose ≥ 11.1 mmol/L can be diagnosed as diabetes mellitus. After 2h of oral glucose tolerance test ≥11.1mmol/L is diabetes, and between 7.8 and ≥11.1mmol/L is abnormal glucose tolerance. Glycosylated hemoglobin and fructosamine were indicators of recent disease monitoring in diabetic patients. Plasma insulin and C-peptide level measurement can help to understand pancreatic β-cell function and guide treatment. (iii) Common complications: Acute complications are commonly ketoacidosis and hyperosmolar non-ketotic coma, while chronic complications often include atherosclerotic cardiovascular and cerebrovascular disorders and peripheral vascular disease, diabetic nephropathy, retinopathy, peripheral neuropathy, and skin lesions. Patients often have frequent infections. (1) Diabetes education is one of the important basic treatment measures. (2) Diet therapy and physical exercise. (3) Oral hypoglycemic drug treatment. 1.Insulin secretagogue: sulfonylureas: glibenclamide, gliclazide, glipizide, glipizide, glipizide, etc.; benzoic acid derivatives: such as regeneronide, nateglinide. 2.Insulin sensitizers: thiazolidinedione derivatives. 3.Biguanide: metformin. 4, alpha-glycosidase inhibitors: acarbose, voglibose, etc. (iv) Insulin therapy: for type 1 diabetes or adult late-onset autoimmune diabetes, diabetes with severe infection, acute complications and chronic complications, perioperative and perinatal period, pregnancy and delivery, secondary diabetes, failure of oral hypoglycemic drugs in type 2 diabetes, etc. (v) Monitoring: Regular monitoring of blood glucose, HbA1C, and chronic complications. Key points of nursing and rehabilitation】 Regular measurement of blood glucose and blood pressure, reasonable diet, exercise and foot care. Prevention】 Low calorie, low salt diet, regular exercise to prevent obesity, change unreasonable lifestyle.