What's My Blood Type | Blood Types

Blood Types
There are four basic types of blood—A, B, AB, and O—each with a positive and negative sub-type. O positive is the most common type, with AB negative being the least common. The letter designation of the blood type indicates which antigens are present in the blood cell. The antigen determines which blood types will join if donated. Types A, B, and AB have their titular antigens, and type O has no antigens. Thus, type O can be joined with any blood type, and is a universal donor.

Blood type also indicates which antibodies are present in the blood cell. The antibodies determine which blood cells the body being will reject. Type A rejects type B; type B rejects type A; and type O rejects both types A and B. Type AB contains no antibodies, so will accept any type of blood.

The positive and negative classifications indicate the presence or absence of Rhesus antigens. Blood cells that contain Rhesus antigens (Rh positive) are designated with a "+"; those without (Rh negative) are designated with a "-." People with Rh positive blood can receive both RH positive and negative blood, but those with Rh negative can only receive Rh negative blood.

With both types of distinction in blood type, receiving the wrong type of blood in a transfusion can result in serious medical complications, even death in some cases. These complications, known as transfusion reactions, may include fever, shortness of breath, bodily aches and pains, rapid heart rate, chills, and low blood pressure, as well as allergic reactions, which could cause itching, hives, wheezing, and, most serious, anaphylactic shock. While transfusion reactions are alarming, they are rarely fatal if treated immediately.

Every 3 seconds someone in the United States needs blood. Donating just one pint of your blood can help save the lives of up to three people. Please consider donating blood today. (You can only donate whole blood once every eight weeks.) More information on blood donation, including donation locations, is available from the Red Cross.

Type	% of Population*	Donates to...	Receives from...
A-	6%	A-/+, AB-/+	A-, O-
A+	34%	A+, AB+	A-/+, O-/+
B-	2%	B-/+, AB-/+	B-, O-
B+	9%	B+, AB+	B-/+, O-/+
AB-	1%	AB-/+	A-, B-, AB-, O-
AB+	3%	AB+	A-/+, B-/+, AB-/+, O-/+
O-	7%	A-/+, B-/+, AB-/+	O-
O+	38%	A+, B+, AB+	O-/+

Blood Terminology
Whole blood: blood in the same form as it exists within the body, with red cells, platelets, and plasma. It's used almost exclusively in instances of severe blood loss.

Red cells: these are used in the treatment of uncorrectable anemia, such as when rheumatoid arthritis, cancer, sickle cell. They're also essential after physically devastating things like surgery, childbirth, and severe burns.

Platelets: used to treat bone marrow failure, post-transplant and chemotherapy treatments, and leukemia.

Plasma: used after obstetric loss of blood (such as childbirth), during cardiac surgery, and to reverse anti-coagulant treatment. It's also used to replace clotting factors after massive transfusions or when they're not being sufficiently produced, such as liver disease.