The oral glucose tolerance test is the gold standard for the diagnosis of diabetes and is also used for the diagnosis of gestational diabetes. The steps of oral glucose tolerance test are as follows: 1. Eat normally for 3 days before the test, and eat no less than 150g of carbohydrates per day. 3 days before the test, stop using drugs that affect blood glucose, such as birth control pills and glucocorticoids, etc. 2. Draw venous blood on an empty stomach on the day of the test to measure venous blood glucose, and insulin and C-peptide can be measured simultaneously. 3. Mix 75g of glucose into 200-300ml The test will be completed within 5 minutes from the first sip of sugar water, and venous blood will be drawn 1 hour after taking sugar and 2 hours after taking sugar to measure venous blood glucose, and insulin and C-peptide can be measured simultaneously. 4. During the test, it is not necessary to be bedridden, no strenuous activity is allowed, a small amount of water can be drunk, and no other carbohydrates or sugary drinks can be consumed.