In the event a person with O positive blood should need a transfusion---due to trauma, surgery, cancer, blood
disorders or other illnesses---he or she can receive
positive or O
negative blood. As a result, O positive blood is in high demand, trailing only O negative blood, which is used in emergencies when there isn't time to type a recipient's blood.
Those who are O positive can donate blood to any of the other positive blood types.