what is a rare blood type
A blood type is considered rare if fewer than 1 in 1,000 people have them. One of the rarest blood types in the world is Rh-null, which lack any antigens in the Rh system.There are only 9 active donors in the community of rare blood donors that have Rh-null blood. Rh-null is considered a âuniversal bloodâ for anyone with a rare blood type within the Rh system.ne of the rarest blood types in the world is Rh-null, which lack any antigens in the Rh system. There are only 9 active donors in the community of rare blood donors that have Rh-null blood.