The O positive blood type is not a rare blood type. It is the most common blood type, according to the American Red Cross. The rarest blood type is AB negative.
The occurrence of O-positive blood types within a population varies depending on the ethnic group. Thirty-seven percent of Caucasians have O-negative blood. For African Americans, 47 percent have the O-negative blood type. Hispanics have the highest percentage of O-negative blood, with 53 percent of the population possessing this blood type. Thirty-nine percent of Asians have O-negative blood. The universal blood donor is O positive, which means that people who possess this blood type may donate blood to any recipient.