To know whether there is diabetes, the main concern is the following: 1. whether there is dry mouth, excessive drinking, excessive urination, unexplained loss of shape, repeated skin boils, repeated urinary system infections, and repeated periodontal swelling and pain; 2. to pay attention to whether blood sugar is elevated. Before doing the examination, fasting and water fasting before 10 pm the night before, and going to the hospital in the morning of the 2nd day to measure venous blood, to judge whether it is diabetes must be based on venous blood as the standard, peripheral blood and glycated hemoglobin are not used as the basis and standard for diagnosis. Generally, venous blood fasting >7.0mmol/L and random blood glucose >11.1mmol/L is the gold standard for the diagnosis of diabetes mellitus. Glucose tolerance test diagnoses diabetes based on fasting blood glucose >7.0mmol/L and 2 hours after taking sugar >11.1mmol/L. On this basis, it is necessary to exclude the presence of recent infections, thyroid system diseases and pancreatic islet function abnormalities that cause elevated blood glucose. The diagnosis of diabetes can be made by excluding the thyroid, pancreas, pain and elevation of blood glucose under stressful conditions.