It is not allowed to drink alcohol the day before blood donation, if you drink alcohol the day before blood donation, it will lead to unqualified blood samples and some adverse reactions in the process of blood donation. 1. Unqualified blood samples: If you drink alcohol the day before you donate blood, especially if you drink a lot of alcohol, the alcohol cannot be completely metabolized in the body, which can cause unqualified blood samples, such as elevated aminotransferases. The blood samples can not be used in the clinic after drinking alcohol, and the blood samples must meet the clinical demand for blood. 2. Some adverse reactions may occur during the process of blood donation: some people who donate blood may experience transient hypotension after blood donation, and donors may experience dizziness, panic and other symptoms. If you drink alcohol or a large amount of alcohol the day before you donate blood, it may aggravate the adverse reactions and symptoms of blood donation, which is unfavorable to the health of the donors. You need to quit smoking and drinking before donating blood and must pass the test before donating blood. If some adverse reactions occur during blood donation, they need to be treated by a physician and should not be treated with medication.