In the daily act of blood donation, the maximum amount of blood donated should not exceed 400ml, because the blood volume of the human body is related to the body weight, generally the weight of blood accounts for 7%-8% of the body weight, converted into volume, the normal blood of adults is around 4200-4500ml, a donation of 400ml, basically reaches about 1/10 of the whole body blood volume, the human body has no obvious discomfort. If the volume of blood donated is too much, for example, reaching 600ml or even higher, the blood volume of the human body will be significantly insufficient after donation, and the donor will experience a series of discomfort such as pallor, dizziness, weakness, palpitations, etc., which will have obvious effects on the donor’s health. For people who are significantly underweight, such as those who only weigh about 55kg, it is best not to donate more than 400ml of blood. 200ml or at most 300ml of blood is usually enough.