Which blood type is considered the universal donor?

The universal donor blood type is O. People with type O blood lack A and B antigens on their red blood cells, which means that their blood can be safely accepted by recipients of any ABO blood type (A, B, AB, or O) without triggering an immune response. This quality makes type O blood particularly valuable in emergency situations where blood transfusions are required quickly and matching blood types is not feasible.

Type AB, on the other hand, is considered the universal recipient because individuals with AB blood can receive A, B, AB, or O blood without adverse reactions; however, they cannot donate to everyone. Blood types A and B have specific antigens that can cause complications if transfused to individuals with other blood types, thus limiting their compatibility in donation scenarios. The unique properties of type O blood are what contribute to its designation as the universal donor.