Generally speaking, blood donation is not particularly harmful to the body, but there is a criterion that people who are physically weak or particularly thin should not donate blood. This is because the overall blood volume of these people is low, and blood donation can easily lead to dizziness and shock, which will be bad for the body. Secondly, it is not good to donate blood too many times as it may lead to iron deficiency. If you donate blood too many times, you need to replenish iron in time, you can eat more lean meat to replenish iron. To some extent, blood donation can also stimulate the bone marrow to produce blood, as long as it is not too frequent. It is generally recommended that people who donate blood are mainly healthy people, that is, people who are physically strong. Blood donation is generally not harmful to the body, but note that there are some people who have infectious diseases, in fact, can not donate blood. For example, China is a large country with hepatitis B. People with hepatitis B cannot donate blood. It is also best not to donate blood if you have a combination of other easily infectious diseases. In addition, do not donate blood during illness, such as the flu, these patients can have some complications if they donate, which can easily lead to low blood pressure, so donating blood is not good for the body, but under other normal circumstances can generally donate blood.