Diabetes is mainly determined by the level of blood glucose. If fasting venous blood glucose >7mmol/L and blood glucose >11.1mmol/L 2 hours after meal, any point that reaches the standard 2 times can confirm the diagnosis of diabetes. If there are also typical symptoms of diabetes such as thirst, excessive drinking, polyuria and wasting, the diagnosis of diabetes can also be confirmed if the blood glucose reaches the standard once. The glucose tolerance test is still the gold standard for diagnosing diabetes, and is performed by taking 75g of glucose, dissolved in 250-300ml of water, orally on an empty stomach in the early morning of the second day, after 8 hours of fasting, and drinking it in 5-10 minutes. The blood glucose is measured half an hour, 1 hour, 2 hours and 3 hours after fasting and drinking glucose water. If the blood glucose reaches the above-mentioned standard in both fasting and 2 hours after meal, the diagnosis of diabetes can be clearly made.