Which blood type is known as the universal donor?

The blood type known as the universal donor is O-. This designation comes from the fact that O- blood does not have A or B antigens on the surface of its red blood cells, nor does it have the Rh factor (which is a positive or negative component). As a result, individuals with type O- blood can donate to any other blood type without the risk of the recipient’s immune system reacting against A or B antigens.

In transfusion medicine, the presence of these antigens is critical because if a patient receives blood that contains antigens their body does not recognize, it can result in a serious immune response, leading to potentially life-threatening complications. Therefore, O- blood is often used in emergency situations when the blood type of the patient is not immediately known, making it very valuable in medical settings.

Other blood types, such as A+, B+, and AB+, have specific antigens that can lead to complications if transfused into individuals with incompatible blood types, which is why they cannot be considered universal donors.