The rarest blood group in the United Kingdom is AB, and as only 15 percent of people are Rhesus (Rh) negative, the rarest type overall is AB negative. The type of blood a person inherits depends on their parents' genetics.
There are four primary blood groups: O, A, B and AB. In addition, people are either Rh negative or Rh positive, this means there are eight blood types present in the population:
- A Rh positive or A Rh negative
- B Rh positive or B Rh negative
- O Rh positive or O Rh negative
- AB Rh positive or AB Rh negative
In the U.K., the most common blood group is O positive, with 44 percent of people carrying it. A further 42 percent have A, 10 percent have B and 4 percent have AB. Around 85 percent are Rh positive, and 15 percent are Rh negative. The type of blood a person has determines what type of blood they can receive and who they can donate to. As O features neither A nor B antigens, it can be donated to anyone. However, this also means O carriers can only receive O blood. In contrast, AB carriers can donate to few people, but they can receive blood from anyone, providing the Rh factor is correct.
Receiving blood from the wrong group can cause the recipient to die as a result of the body generating life-threatening antibodies. Someone who is Rh negative should also receive Rh negative blood.