It is better not to drink a lot of water before the routine blood test, because the routine blood test is to check the number, shape and ratio of various blood cells in the peripheral blood of the patient by drawing the peripheral blood, and through these tests to understand whether the patient’s body functions normally. If the blood is diluted after drinking water, especially in large amounts, the patient’s hemoglobin concentration and platelet count, as well as the number of white blood cells, may decrease due to blood dilution. If a large amount of water is consumed and the blood is diluted, the hemoglobin concentration may drop to 110g/L, which may mislead the doctor into thinking that the patient has anemia, so it is best not to drink a lot of water before the blood test.