What is a Blood Transfusion?

A blood transfusion is a safe and common procedure. Most people who have a bone marrow failure disease like aplastic anemia, MDS or PNH will receive at least one blood transfusion. When you receive a blood transfusion, the cell parts of blood from a donor are put into your bloodstream. This can help some patients with low blood counts.

The U.S. Blood Supply

The U.S. blood supply is among the safest in the world, according to the CDC (U.S. Centers for Disease Control and Prevention). Blood collected in the U.S. is checked carefully for diseases like HIV (the virus that causes AIDS) and hepatitis. Any blood and blood products that have these diseases are safely discarded and are not used. At this time, the risk of getting an infection in the United States through getting a blood transfusion or blood products is extremely low.

A transfusion usually involves only certain parts of blood. These might be the red blood cells, platelets or plasma. Rarely is whole blood (red cells, plasma, platelets, and white cells) used for a transfusion. Learn more about blood and bone marrow basics.

The parts of blood used for any transfusion should match the patient’s blood type for red blood cell transfusions. Otherwise, antibodies in the patient’s blood may attack the transfused blood. This can make the patient sick. Matching blood types is less important for other components such as platelets and plasma, where most of the red blood cells have been removed.

Blood types are based on substances (antigens) on the blood cells. The blood used for any transfusion has to be compatible the patient’s blood type. Otherwise, antibodies in the patient’s blood will attack the transfused blood and make the patient sick. Every person has one of four groups of blood: A, B, AB, or O. These blood types are known as the ABO blood type. They indicate whether the patient has antigen A, antigen B, both antigen A and antigen B, or neither of these antigens.

Blood is also Rh-positive or Rh-negative. This means that the patient either has the Rh D antigen or doesn’t have it. The blood of someone with type A blood that is Rh-positive is referred to as type A-positive blood.

Blood type matching is particularly important for red blood cell transfusions. It is typically not critical for platelet or plasma transfusions and most people who receive platelet or plasma products that are of a different type should not have problems.

The transfusions that are safe for each ABO blood type are as follows:

  • Type A red blood cells: Safe for people with type A or AB blood
  • Type B red blood cells: Safe for people with type B or AB blood
  • Type AB red blood cells: Safe for people with type A, B, or AB blood
  • Type O red blood cells: Safe for people with type A, B, AB, or O blood

Safe transfusions by Rh status are as follows:

  • Rh-positive red blood cells: Safe for people with Rh-positive
  • Rh-negative red blood cells: Safe for people with Rh-negative or Rh-positive red blood cells