For patients who have a need for fasting examination the next day, it is common to fast from food and water after 10:00 pm to avoid affecting the examination results. For normal people, it is not recommended to drink a lot of water after 9 pm. It is not recommended to drink a lot of water after 9 pm, but not in the absolute sense of not drinking water. People after 9 pm, glomerular filtration function decreases, a large amount of water may increase the burden on the gastrointestinal tract and kidneys, but also increase the burden on the heart, which in turn affects the physiological state of the body, the appearance of ocular and lower limb edema. At the same time, drinking large amounts of water at night before going to bed may lead to frequent waking up, affecting the patient’s sleep quality, which in turn affects the patient’s work and life the next day. In short, a normal day of drinking water in addition to the water obtained in the diet, drinking 2000ml of water can be, more than recommended in the daytime a small number of times of hydration, a glass of warm water in the morning can promote gastrointestinal peristalsis, try to avoid a lot of water after 9 pm.