Drinking a small amount of water at night generally does not affect the morning fasting blood glucose measurement, while drinking a large amount of water may affect the morning fasting blood glucose measurement. When measuring fasting blood glucose on day 2, drinking a small amount of water the night before does not usually dilute the blood glucose, so the effect on the test results is relatively small and generally does not require excessive concern. However, if you drink a large amount of water during the night, it may cause some dilution of blood glucose, in which case it may affect the accuracy of fasting blood glucose and make the test results less accurate. The night before the fasting blood glucose test, be careful not to drink or eat a lot of water, fasting for at least 8 hours or more, drinking water need to choose pure water, mineral water and other non-calorie, no sugar water, avoid drinking cola and other sugary drinks. Before checking fasting blood glucose, you need to strictly follow the doctor’s instructions to prepare, so as not to affect the test results.