All About Blood Types

4. Rare Blood Types

Beyond the eight most common, there are several rare blood types. Because there are so many antigens in blood, the presence or absence of some of these antigens creates a rare blood type. For example, a person with no Rh antigens at all has type Rh null. A blood type counts as rare if fewer than one in 1,000 people possesses it. Some blood types are unique to racial or ethnic groups. Those with rare blood types will often bank their own blood because there is a lack of supply for transfusions.