In order for a blood transfusion to be safe and effective, it’s important for the donor and the recipient to have blood types that go together. That’s because the person receiving the transfusion has antibodies that will actually fight the cells of the donor blood, causing a toxic reaction. Now experts know that if you mix blood from two people with different blood types, the blood can clump, which may be fatal. Before that, doctors thought all blood was the same, so many people were dying from blood transfusions. You either have this antigen (meaning your blood type is “Rh+” or “positive”), or you don’t (meaning your blood type is “Rh-” or “negative”).īlood groups were discovered in 1901 by an Austrian scientist named Karl Landsteiner. The third kind of antigen is called the Rh factor. Group O doesn’t have A or B antigens but has both A and B antibodies. Group AB has A and B antigens but neither A nor B antibodies. Group B has the B antigen and the A antibody. Group A has the A antigen and B antibody. Doctors call this the ABO Blood Group System. The four major blood groups are based on whether or not you have two specific antigens - A and B. O negative: Someone with this rare blood type (6.6%) can give blood to anyone with any blood type. Someone with this can give blood to anyone with a positive blood type. O positive: This is one of the most common blood types (37.4%). Someone with this blood type is known as a “universal plasma donor,” because anyone can receive this type of plasma. They’re known as universal recipients.ĪB negative: This is the rarest blood type - only 0.6% of the U.S.

population) can give blood to anyone with A or AB blood type.ī positive: Someone with this rare type (8.5%) can give blood only to people who are B positive or AB positive.ī negative: Someone with this very rare type (1.5%) can give blood to anyone with B or AB blood type.ĪB positive: People with this rare blood type (3.4%) can receive blood or plasma of any type. Someone with this type can give blood only to people who are A positive or AB positive.Ī negative: Someone with this rare type (6.3% of the U.S. A positive: This is one of the most common blood types (35.7% of the U.S.