How common is B-positive blood?

B-positive blood occurs in 9 percent of the Caucasian population, 18 percent of the African-American population, 9 percent of the Hispanic population, and 25 percent of the Asian population in the United States, according to the Red Cross. Type B blood is donated to AB types and B types.

Blood type is determined by the presence or absence of particular antigens. Blood with different antigens causes the transfusion recipient's body to attack the transfused blood. This is why blood is carefully categorized and cross-matched, according to the Red Cross. Type O blood is the most common. It can be transfused to all other blood types.