Why do we need to donate blood for a transfusion for my father, whose blood type is O-negative?
The O-negative blood type is referred to as the "universal donor," because people of all blood types can receive O-negative blood. This means it's much in demand--but it's not a very common blood type.
Furthermore, people with O-negative blood can't receive blood from people who have any other type, because all other blood types have either the A and B antigens or the Rh factor. This can cause a transfusion reaction in O-negative people, which can be serious. If you and your family members already know that you're also O negative, your father's doctor is probably thinking that it will be safest for him to receive your blood to prevent any mismatch. Also, although the public blood supply is considered completely safe, many people still prefer to donate blood within the family.
