Blood Type Genetics and Compatibility

There are four main blood types: A, AB, B and O. AB positive is considered the universal recipient, and O negative is considered the universal donor.

Blood type frequency (U.S. population)

• O Positive blood—37%
• O Negative blood—7%
• A Positive blood—36%
• A Negative blood—6%
• B Positive blood—8%
• B Negative blood—2%
• AB Positive blood—3%
• AB Negative blood—1%

Blood type compatibility

Your ABO blood type is based on the presence or absence of the A and B antigens on your red blood cells. The A blood type has only the A antigen and the B blood type has only the B antigen. The AB blood type has both A and B antigens, and the O blood type has neither A nor B antigen.

By the time you are 6 months old, you naturally develop antibodies against the antigens your red blood cells lack. For instance, a person with A blood type will have anti-B antibodies, and a person with B blood type will have anti-A antibodies. If you have type A blood, you cannot receive B blood because your body's anti-B antibodies will fight the B blood's B antigens. It is crucial we have all blood types available to our patients.