Normal and moderate amount of blood donation has no effect on the body, but excessive blood donation at one time or frequent blood donation may have the effect of dizziness and discomfort, anemia, and increase in the brittleness of blood vessels. 1. Normal and appropriate amount of blood donation is a donation of 200~400m of blood, the interval between donations is not less than 6 months, and people who donate 400ml of blood can’t donate for the second time within half a year, in this case, blood donation won’t have any effect on the body, and it can also promote the hematopoiesis of bone marrow. 2. Dizziness and discomfort: donating a large amount of blood at one time will lead to a reduction in peripheral blood volume and a corresponding reduction in blood supply to the brain, resulting in insufficient blood supply to the brain and dizziness and discomfort in the absence of oxygen. 3. Anemia: long-term large-scale blood donation, the organs of the blood loss of the compensatory effect of the gradual decline in blood production capacity will also gradually decline, may trigger the body anemia, with pale, decreased appetite, mental depression and other symptoms of discomfort. 4. Increased brittleness of blood vessels: People who donate blood frequently may reduce the elasticity and ductility of blood vessels. Whether you can donate blood should be decided after checking your health first to minimize the impact on your body.