Don’t drink water in the morning before drawing blood, especially don’t drink a lot of water, no matter what kind of test, drinking water before drawing blood will cause some interference with the test results. For example, if you drink water before doing routine blood tests, after the water is absorbed into the body, the blood is diluted, and the density of blood cells will decrease, such as the density of red blood cells decreases, the concentration of hemoglobin decreases, and the routine blood tests may cause the patient to have the false impression of anemia. When doing biochemical tests, such as checking liver function, if you drink water before drawing blood, it may also cause inaccurate transaminase measurements. When doing serological tests, such as checking the titer of various viral antibodies, if you drink water before drawing blood in the morning, the serological test results will show a drop in titer, which will cause some interference with the test results, so don’t drink water before drawing blood in the morning.