"If there is anything that I would hope all potential blood donors know, it is that they are walking around with the most important commodity in the world. We can't manufacture it and for patients who need your blood type, you are the only source of this lifesaving gift." - A Trauma Center Physician.

Blood: What’s Your Type?
Q. What is a blood type?

A. When we talk about blood type, we are usually referring to the typing of red cells. We are looking for the presence or absence of the A or B antigen, and the Rh (or D) antigen, a protein substance which is found on the surface of the red cell. (If you are type O, you lack both the A and the B antigen.) These are the most common antigens. In addition, there are nearly 600 other red cell antigens.

Q. What's the most common blood type?

A. ABO Rh typing is performed on all whole blood donations. Here is how often each type occurs in the general population:

Q. Why is blood typing important?

A. When our bodies are exposed to something foreign, like a blood transfusion, our immune system kicks in to protect us. One weapon the body uses is the production of antibodies, protein molecules released by plasma cells that bind to a specific antigen. The antibodies couple with the antigens on the surface of the invading cells and try to destroy the cells. We cross match a donor's blood with a patient's blood to prevent this kind of reaction, which can range from mild to very serious. Antigens are also found on white cells and platelets. Testing, such as HLA testing, may be performed.

Q. What is alloimunization?

A. Most of us will only need blood at one time in our lives, to help fight a disease, because of an injury or for surgery. But some patients, like sickle cell disease patients, may need blood many times during their lives. If the blood they receive is not a very close match, they can begin to develop antibodies against the donated blood. This is called alloimunization, and it means that an important source of help and hope will be gone. To prevent that, blood for these patients should be closely matched. Often, this will be an uncommon blood type. For sickle cell disease patients, the best match will come from donors of African descent. Fully one third of requests for rare blood received by the Red Cross is for a blood type found exclusively among African Americans.

Q. What is a rare blood type?

A. Some patients require rare blood types found in only one in 1,000 donors, or even less frequently. Through the American Rare Donor Program we identify donors who have these rare blood types and ask them to let us list them in our registry. When a need for their special blood type arises, we can call upon this donor to give. Red Cross also freezes some rare units of red cells which can be stored for up to ten years to assure their availability in time of need.

If you are asked to join this registry, please say yes. Someone, somewhere needs what you, and only you, may be able to give. Rare blood may be sent anywhere in the world to help a patient.

Q. What is the universal donor?

A. Type O donors are known as universal donors because their red blood cells may be transfused to patients of any other blood type in an emergency situation or if the needed blood type is unavailable. Because any patient can receive O negative red blood cells, there is a need for O donors to give more often and shortages of type O blood are very serious. Type AB plasma can be given to anyone as well. But whatever your blood type, you are important to someone!