Drinking water before the physical examination may affect the blood indicators, such as blood sugar and blood lipids. After drinking water, the body will absorb the water solution drunk, thus diluting the blood, so it will indirectly affect the indicators of the test. Drinking water will also have an effect on the urine routine, because after drinking water, it will not be filtered through the kidneys to get more accurate urine tests, such as whether there is infection in the urine, whether there is protein or red blood cells or white blood cells. Drinking water can also affect the abdominal ultrasound. After drinking water, it can affect the ultrasound exploration of the whole digestive system during the ultrasound. Therefore, before the physical examination, the doctor will tell the four hours or so to try not to drink water, so as not to affect the various examinations.