The administration of blood or its components as a part of a medical treatment. There are certain fairly well-delineated indications for the use of some form of transfusion. Hemorrhage, severe burns, and certain forms of shock are perhaps the most important conditions for which blood transfusion is utilized. Other disorders in which hemotherapy may be indicated include hemophilia, leukemia, certain anemias, and rare hereditary or familial disorders in which some portion of the blood is lacking or deficient.