2. Some physical examination items require that you can't drink water, such as barium meal examination of upper digestive tract. After drinking water, barium sulfate can't stay in the stomach, which leads to the failure of the examination. You can't drink water during gastroscopy. Drinking water will affect the visual effect under the microscope. You don't need the above items when you apply for a health certificate. In general, you can drink water. Try to go to the hospital on an empty stomach in the morning and bring your ID card. It should be noted that you need to have a stool examination.