Which blood type is likely considered a universal donor?

The blood type that is considered a universal donor is O-. This designation stems from the fact that individuals with O- blood type do not possess A, B, or Rh antigens on the surface of their red blood cells. Because of this lack of antigens, O- blood can be transfused into individuals of any blood group without the risk of an immune reaction.

Transfusions that involve A or B antigens present particular challenges, as individuals who are A or B blood type may have antibodies against the opposite antigens. For example, a person with type A blood has anti-B antibodies and would react negatively to type B blood. In contrast, type O- blood does not provoke an immune response in recipients of any other blood type, making it ideal for emergency situations where blood type compatibility may not be known.

While O+ is also frequently referred to as a universal donor in some contexts due to its prevalence, it does have the Rh antigen, which can cause complications in Rh-negative recipients. Therefore, O- remains the safest and most universally acceptable choice for donation across all blood types.