Glucose tolerance requires a minimum fast of 8 hours. The glucose tolerance test should be performed with a fast starting at 21:00 the night before the test, for at least 8 hours, and the test must be performed between 7 and 9 am that morning.
The 8-hour fast is to ensure the accuracy of the test results. Blood from a vein when tested after 8 hours of fasting ensures accuracy. If you eat or drink a lot of water, you will produce new energy or dilute the blood, and these factors can lead to grossly inaccurate test results. However, at this time, if you are seriously thirsty, there is no problem to properly quote 50ml of plain water, which can serve as a throat moistener, but not tea, sugar water, etc.
The longer you fast, the better. Don’t be afraid that your blood sugar level will rise, so you deliberately start starving yourself very early, which is also unnecessary. The human organism has a strong ability to self-regulate, and when in a fasted state for a long time, it can also cause distortion of the test results. It may cause the numbers to look normal while masking the true results.