Who am I?

What is your blood group?

The ABO system is based on two different antigens, A and B, found on the surface of red blood cells. You may have one, both or neither of these antigens. Group AB people, the least common in the UK, have both. Group O, the most common, have neither. If you were to receive blood that contained an unfamiliar antigen, antibodies in your own blood would clump the donated cells together and you would die.