AB- is the rarest of the commonly recognized blood types, though the extremely rare Rh-null type is the rarest of all blood types. A blood type is considered rare when fewer than one in 1,000 people carry it.
There are eight common blood types, which are each determined by the presence or absence of specific antigens. There are 35 recognized blood groups with over 600 known blood group antigens. Blood types are also referred to as blood groups. The most common blood type is O positive.
Blood type is an inherited feature, like eye color, which is passed genetically from parent to child. Certain blood types are characteristic of specific ethnic groups.
Some blood transfusion patients require a closer blood match than that provided by the typical ABO positive and negative blood typing. Those with Rh-null blood, which lacks any antigens, can only receive Rh-null blood. Rh-null blood was first documented in 1961. As of 2010, only 43 people with Rh-null blood had been documented worldwide ,and only 9 were listed as blood donors. Rh-null blood is the universal blood for anyone with a rare blood type within the Rh system.