In general, the maximum amount of blood donated should not exceed 400ml, because if the amount of blood donated exceeds 400ml, it may have certain effects on the health of the donor, who may experience a series of uncomfortable symptoms such as pale face, dizziness and weakness after donating blood. The amount of blood in the human body is proportional to one’s own body weight. Generally speaking, the weight of blood in the body accounts for 7%-8% of one’s own body weight, the heavier the body weight, the more blood in the body, and the lighter the body weight, the less blood in the body. For a person weighing about 70kg, the general body blood is between 5.0-5.5kg, which is between 5000ml and 5500ml. If the blood donation does not exceed 400ml, there is generally no significant effect on the human body. If it exceeds 400ml, the amount of blood donated is close to 1/10 of the total amount of blood in the body, and a series of uncomfortable symptoms will easily occur, so generally do not exceed 400ml when donating blood.