Glucose tolerance is also known as glucose tolerance test, which is done clinically mainly to diagnose diabetes, gestational diabetes and so on. You can eat normally three days before the test, fast after 12:00 p.m. the night before the test, and fast for 8 to 10 hours before the test. It is usually performed during the 24th to 28th week of pregnancy. On the day of the test, you need to take the first blood draw in a fasting state, then drink 250-300ml of sugar water containing 75g of glucose within 5 minutes, counting from the first sip of the sugar water, and then take another blood draw in the following 30 minutes, 1 hour, 2 hours, and 3 hours respectively. Pregnant women are usually tested for blood glucose on an empty stomach and 1 hour and 2 hours after drinking sugar water. The glucose tolerance test needs to be conducted under the guidance of a doctor and the results need to be analyzed by a medical professional.