Do gastroscopy is generally not need to drink laxatives, gastroscopy does not need to clear the bowel, do colonoscopy only need to use laxatives to empty the intestine, usually with compound polyethylene glycol electrolyte bulk (Ⅱ), sodium phosphate oral solution or mannitol, etc., usually in about half an hour after taking it will take effect. It is necessary to fast for 6 to 8 hours to do gastroscopy, and you must have an empty stomach to do gastroscopy, because if there is food in the stomach, it will affect the observation. However, gastroscopy does not require purging and laxatives because having something inside the intestines does not affect gastroscopy, and if gastroenteroscopy is done at the same time, purging is required. If you have had a barium meal before gastroscopy, you need to wait for the barium to empty before doing gastroscopy. If you have pyloric obstruction, you need to fast for 2 to 3 days before gastroscopy, and if necessary, you need to wash the stomach to remove all the food left in the stomach. If you are doing colonoscopy is required to take a laxative, laxatives are usually taken on the first night, taking half an hour or so will begin to diarrhea, you need to wait for the discharge of watery stools before doing the examination.