The rarest blood type in the world is the Rhnull blood type, often called the "golden blood" type. Only about 1 in every 6 million people have Rhnull blood, and fewer than 50 individuals worldwide are known to have this blood type. Rhnull is unique because it lacks all Rh antigens on the red blood cells, unlike other blood types that have some or all Rh antigens. This makes it incredibly rare and precious in transfusion medicine. People with Rhnull blood can donate to anyone with rare Rh blood types, but they can only receive blood from other Rhnull donors, making transfusions challenging. Other rare blood types include AB-, which is the rarest of the eight common blood types, and the Bombay blood group, which is very rare in certain populations. However, Rhnull remains the rarest and most unique blood type known.
Additionally, a newly discovered blood type called Gwada-negative has been identified as extremely rare, with only one known individual having it worldwide. This blood type is characterized by a unique genetic mutation affecting red blood cell antigens, presenting even greater challenges for blood compatibility and transfusion.
