Here we break down what the different blood types are and what they mean for donating purposes.
Why do we have different blood types?
The blood group you belong to depends on what you have inherited from your parents. According to the South African National Blood Service (SANBS), currently there are more than 20 blood group systems that exist, but the AB0 and Rh blood group systems are the most important ones used for blood transfusions.
The differences in human blood are due to the presence or absence of certain protein molecules called antigens and antibodies. The antigens are located on the red blood cells and the antibodies are in the blood plasma. Individuals have different types and combinations of these molecules.
Not all blood groups are compatible. Mixing incompatible blood leads to clumping or agglutination, which is very dangerous for individuals.
What are the different blood types and what do they mean?
All donors belong to one of four blood groups: A, B, AB or O. You are also classified as either Rh+ or Rh-.
A person with Rh- blood does not have Rh antibodies naturally in the blood plasma. But a person with Rh- blood can develop Rh antibodies in the blood plasma if he or she receives blood from a person with Rh+ blood. A person with Rh+ blood can receive blood from a person with Rh- blood without any problems.
There are therefore eight different main blood groups, ie: A+, A-, B+. B- and so on.
Not all blood groups are compatible with each other and the success of modern transfusion medicine depends on classifying and matching donors and patients correctly.
The South African government states that O+ is the most commonly found blood type in SA and that the rarest is AB-. Blood type O is also universal, which means it can be given to all the other blood types. Currently South Africa is experiencing a critically short supply of blood type O. While we have a greater stock of B+, this blood can only be given to B and AB blood types.
Visit RedCross.org for interactive graphs on how compatibility works.
June 14 is World Blood Donor Day. Click here to do a quick quiz and find out more about how you can save 3 lives with one donation.