Diagnosis of the presence of diabetes in 1999 WHO (World Health Organization) announced new criteria for the diagnosis of diabetes, which were endorsed by the Chinese Medical Association Diabetes Society and officially implemented in China. Those who have symptoms of diabetes (polyuria, irritable thirst, excessive drinking and wasting) meet one of the following three criteria: 1. Random (any time of the day) plasma glucose ≥ 11.1mmol/L. 2. Fasting plasma glucose ≥ 7.0mmol/L. 3. Oral glucose tolerance test (OGTT) two-hour plasma glucose ≥ 11.1mmol/L. Diagnostic instructions: 1. Asymptomatic people Diagnosis of diabetes mellitus should have two blood glucose measurement results meeting the above criteria. 2.In acute infection, trauma, surgery or other stressful situations, although significant hyperglycemia is measured, it cannot be immediately diagnosed as diabetes, and should be retested after the stressful situation is over. If for some reason OGTT is not suitable, or if the child has heavy diabetic symptoms, high blood sugar, positive urine glucose or positive urine ketone bodies, OGTT may not be performed. Diagnosis of which type of diabetes: 1. Type 1 diabetes: absolute lack of insulin due to destruction of pancreatic beta cells, with a strong genetic predisposition. It usually starts before the age of 18, is mostly wasting, has an acute onset, has obvious diabetic symptoms, and requires insulin therapy to control the disease. Patients often present with ketosis, positive urine ketone bodies, low or even undetectable blood insulin and C-peptide levels, and persistent positive antibodies to pancreatic beta cells in the body. Adult occult autoimmune diabetes mellitus is a subtype of type 1 diabetes mellitus, which is characterized by adult onset, slow progression, non-insulin dependent at early stage, non-obese at onset, low blood insulin and C-peptide levels, persistent positive pancreatic β-cell antibodies, and susceptibility gene of type 1 diabetes mellitus. Type 2 diabetes mellitus: insulin resistance is mainly accompanied by insufficient insulin secretion, or insufficient insulin secretion is mainly accompanied or not accompanied by insulin resistance. It accounts for more than 90% of all diabetic patients, and its etiology is now considered to be promoted by a combination of polygenic genetic and environmental factors (mainly lack of exercise and relative excess energy), with race, family history, poor lifestyle, obesity (especially abdominal obesity), dyslipidemia, old age and abnormal glucose tolerance as its risk factors. 3.Other special types of diabetes: including a series of diabetes of clearer etiology or secondary, caused by genetic defects, other endocrine diseases, drugs and chemicals, infections, etc. 4. Gestational diabetes: diabetes that occurs or is first detected during pregnancy. The screening time is usually chosen between 24-28 weeks of gestation. For gestational diabetes patients should be re-tested for glucose tolerance 6 weeks or longer after delivery, most patients may return to normal blood glucose, but their chances of developing diabetes can increase significantly after some time. Diagnosis of the presence of complications Acute complications of diabetes include mainly: diabetic ketoacidosis, diabetic hyperosmolar coma, lactic acidosis, and hypoglycemic coma. Chronic complications of diabetes include macrovascular disease (e.g., coronary artery disease, hypertension, etc.), diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, diabetic foot, etc.