What types of blood can be transfused to the individual whose blood types is unknown?

In emergency situations where an individual's blood type is unknown, type O negative blood is often used for transfusions. Type O negative blood is considered the universal donor because it does not have A, B, or Rh antigens on the surface of the red blood cells, making it compatible with all blood types. However, in non-emergency situations, it is ideal to determine the individual's blood type before transfusing blood to ensure compatibility and reduce the risk of adverse reactions.

O-negative (universal donor)