You should not drink water before the blood test in the morning. If you drink water, the blood will be diluted. When checking the blood routine, the white blood cells, red blood cells and platelets, as well as other cells in the blood routine, mainly rely on the count to reflect the value. If you drink water, these values may decrease significantly, thus affecting the test results. In addition, drinking water will have an effect on the body’s blood glucose, usually after drinking water, blood glucose will increase, so the blood glucose test value is not very accurate. Drinking water can also affect the human liver, liver function tests will be slightly higher, and transaminase tests may also change. Therefore, the morning blood draw should be done on an empty stomach.