Do not drink water before blood glucose test, because blood glucose test is to test the concentration of glucose in blood, and the concentration of glucose will be affected by the blood volume. If you drink water before the blood test, especially after drinking a lot of water, the water will be absorbed into the body, the blood volume will increase, and the glucose concentration will drop, so the measured glucose value will be lower than the actual value, which will affect the doctor’s judgment, so you should not drink water before the blood glucose test. In addition, in addition to not drinking water before the blood sugar test, you cannot eat, because after eating, various nutrients in food, including protein and starch, will be absorbed into the body, especially starchy substances into the body will become glucose, so that the concentration of glucose in the blood will increase, so that the test will appear high blood sugar, affecting the judgment. So you can’t drink water or eat before you want to test your blood sugar.