Glucose tolerance, or glucose tolerance test, is one of the maternity tests and is recommended to be done no later than 28 weeks of pregnancy. Glucose tolerance test is to test the insulin reserve function of pregnant women and a kind of responsiveness to the glucose load, and is also a way to diagnose gestational diabetes. It is appropriate to perform the glucose tolerance test between 24 and 28 weeks of pregnancy, and no later than 28 weeks. During pregnancy, fasting blood glucose should be 5.1 mmol/L or less, 1-hour blood glucose <10.0 mmol/L after taking 75 grams of dextrose water, and 2-hour blood glucose <8.5 mmol/L. If any of these values exceeds the reference range, it is considered gestational diabetes mellitus. Glucose tolerance test is recommended to be performed at 24-28 weeks of pregnancy. The more timely the glucose tolerance test is, the more it can help to detect the problem and prevent gestational diabetes from causing harm to the fetus and the pregnant woman. Gestational diabetes is prone to cause giant babies, miscarriages, difficult deliveries, etc. It is easy to cause cardiovascular and cerebrovascular damage, kidney function damage, etc. Once diagnosed with gestational diabetes, it is necessary to strictly comply with the doctor's instructions to carry out dietary control and insulin and other medication, to prevent the harm caused by gestational diabetes. If you feel unwell, consult a doctor in time.