The glucose tolerance test is performed by drawing a fasting intravenous blood glucose before taking glucose, timing the glucose from the first sip of sugar, and testing the blood glucose 2 hours after taking sugar for the diagnosis of diabetes mellitus. The glucose tolerance test is still the gold standard for the diagnosis of diabetes mellitus, and if there are three more and one less symptom at the same time, and the result suggests that the fasting blood glucose >7mmol/L, blood glucose after taking glucose 2h >11.1mmol/L, and one of them reaches the standard, then diabetes mellitus can be diagnosed. However, the clinical assessment of insulin secretion is often carried out at the same time, so venous blood glucose and insulin are taken at 0.5h, 1h, 2h and 3h after taking sugar, and venous blood glucose needs to be taken 5 times in the whole process. It should be noted that the day before the glucose tolerance test, do not eat after 10:00 p.m., and the day of the blood draw should be performed on an empty stomach and in a resting state. You can walk around appropriately during the blood draw, but you must avoid strenuous exercise, and you should not eat or drink during the whole process of blood draw.