You are not allowed to eat for 6-8 hours before a gastroscopy. Gastroscopy is an invasive procedure that involves placing a camera-equipped endoscope inside the stomach to observe the stomach. If there is food in the stomach, it will affect the clarity of the lens. The presence of food in the stomach also changes the color and shape of the gastric mucosa, thus affecting the accuracy of the test results. Once there is food in the stomach during the implantation of gastroscopy, nausea, vomiting and even choking may occur in some people. After eating food on the first night before the gastroscopy, you should stop any food intake to improve the accuracy of the test. In addition to not being able to eat, you should not drink a lot of water before the gastroscopy. Drinking water dilutes the digestive juices and affects the color of the digestive mucosa, and it also affects the concentration of the digestive juices in the stomach, which can affect the results of the test when extracting the digestive juices.