The best time to have a glucose tolerance test is between 24-28 weeks of pregnancy. After pregnancy, due to the influence of hormone levels in the body, most pregnant women will have insulin resistance and are prone to abnormal glucose metabolism. Glucose tolerance is to check the glucose metabolism of pregnant women. After 24 weeks, it belongs to the rapid growth period of the fetus, the placenta’s secretion function is strong, and various factors affecting glucose metabolism in pregnant women’s body are most obvious, so it is easiest to detect abnormalities and the screening and diagnosis rate is higher during this period. Moreover, if a pregnant woman is found to have abnormal glucose metabolism, early intervention and treatment can be provided to avoid adverse pregnancy outcomes and minimize the harm to mother and fetus. After 28 weeks of pregnancy, as the internal environment of the pregnant woman’s body is in a relatively stable state, the ability of glucose metabolism also tends to be stable, and gestational diabetes is less likely to occur again.