If blood is drawn for a general medical examination it will not cause anemia. The amount of blood in the human body is about 70-80ml/Kg, about 80ml/Kg for men and 70-75ml/Kg for women, so the amount of blood is more for men. The amount of blood drawn for a general medical checkup is about 2ml or 4ml, and for a person weighing 50Kg, there is about 80ml of blood per kilogram, so the total amount of blood is about 4000ml, so drawing 2ml, 4ml, 8ml or 10ml from 4000ml of blood will not cause anemia. However, there are also special blood draws, such as blood cultures when resuscitating critically ill patients. The requirement for blood culture is to draw 5-10ml per tube and 4 tubes in a row, so 30-40ml of blood may be drawn. If the fever is still present on the second day after the blood draw, the blood will be drawn again, so that the blood draw will reach 100-120 ml in 3-4 days. medically induced anemia is a problem, but this is very rare, and blood draws for general medical examinations will certainly not cause anemia.