Before gastroscopy, you need to fast for 6 to 8 hours, smokers should preferably abstain from smoking for about three days, and sedatives can be used if necessary. Gastroscopy is a type of examination in which a gastroscope with a lens is inserted through the mouth into the esophagus, stomach, and duodenum and the mucous membranes are observed. It can detect a wide range of gastrointestinal diseases. If the gastroscopy is done in the morning, it is best to eat a liquid meal or other easy-to-digest food for dinner the day before, do not eat after 8:00 p.m., and do not drink water after 12:00 p.m. If the gastroscopy is done in the afternoon, the patient needs to calculate the time by himself, and should abstain from food and water for 6~8 hours before the examination. If the patient’s gastric emptying time is relatively slow, he/she should fast for a longer period of time. If the patient has pyloric obstruction, gastric lavage can be performed before the examination. Since smoking will stimulate gastric acid secretion, it is recommended to abstain from smoking for 3 days. Sedation may also be given if the patient is too nervous before the gastroscopy. Patients with gastric outflow tract obstruction may undergo gastrointestinal decompression before the examination. If you need to apply defoamer and local anesthesia drugs before the examination, you should go to a regular hospital and follow the doctor’s instructions to make good preparations before the examination.