Glucose tolerance is a test to determine the presence of diabetes mellitus. Glucose tolerance, also known as oral glucose tolerance test, is a diagnostic test to determine the presence or absence of diabetes. It is usually performed by an endocrinologist based on the results of a blood test. For the oral glucose tolerance test, 75 grams of glucose is taken after the blood is drawn on an empty stomach, and then the blood is drawn half an hour, one hour, two hours and three hours after the glucose is taken. Then according to the value of blood glucose, to clarify the state of blood glucose, whether it is diabetes or pre-diabetes or normal people. If a pregnant woman does glucose tolerance can also go to the obstetrics, obstetrics will be based on the results of oral glucose tolerance test to determine whether it is gestational diabetes. The diagnostic criteria for gestational diabetes are more stringent than for the general population.