Precautions before the blood test are the following: 1. fast after 8 p.m. and avoid drinking large amounts of alcohol. 2. do not do strenuous exercise in the morning of the blood test. 3. do not overexert yourself and pay attention to getting enough sleep. 4. do not wear very thick clothes, wear lighter clothing. 5. pay attention to relaxing when taking blood to prevent fear and tension from causing vasoconstriction and increasing the difficulty of taking blood. 6, You can prepare candy before the blood test, and if you eat after the blood test, you can supplement the candy. 7, after the blood test to press the local, do not rub, to prevent the formation of local bruising phenomenon.