The oral glucose tolerance test (OGTT) is not restricted to diet for the first three days, and the fasting starts after dinner before the test, not less than 8-10 hours. 75g of glucose powder is dissolved in 200-300 ml of water during the test, and the test is finished within 5 minutes starting from the first sip of sugar water, and then venous blood is drawn at 30, 60, 120 and 180 minutes after drinking the sugar water, respectively. The steamed bun meal test is similar to the OGTT, but the steamed bun meal test is performed with 100g of standard steamed buns instead of 75g of glucose, and the steamed bun meal test is used when the patient cannot tolerate or is not in a position to do the glucose tolerance test.