A, B, O and AB are the four main blood groups. Learn more about each type and its importance in the community.
What determines someone’s blood type?
Our different blood types are determined by the presence or absence of certain antigens (unique substances) on the surface of our red blood cells. These antigens are an important part of blood donation and transfusion because patients cannot receive red blood cell transfusions from donors that have different antigens than their own red blood cells. Our body produces antibodies (part of our immune response) against antigens that are “foreign” to our body – thus limiting the blood types that patients can receive for transfusion.
While there are many different types of antigens on our red blood cells and throughout our body, there are 2 main blood antigen groups that determine our blood type: ABO and Rh.
ABO blood group
The A and B antigens, and their presence on our red blood cells determines if our blood type is O (lacks both A and B antigens), A (has the A antigen only), B (has the B antigen only), or AB (has both A and B antigens).
Rh blood group
The presence or absence of the Rh antigen determines whether we are (+) or (-).
Therefore, the 8 blood types are the following: O+, O-, A+, A-, B+, B-, AB+, AB-
Learn more about the genetics of how blood type is inherited.