Which type of blood is considered universal donor?

Type O, Rh-negative blood is considered the universal donor because it lacks both A and B antigens on the surface of red blood cells. This absence allows O-negative blood to be transfused to individuals of any blood type without the risk of an immune reaction due to ABO incompatibility.

In the case of Rh factor, Rh-negative blood is also crucial since it does not contain the Rh antigen. This characteristic makes it safe to donate to Rh-positive individuals as well, who can generally accept blood from Rh-negative donors without adverse effects.

While O-positive blood can be donated to many people, it still contains the Rh antigen, which limits its universal donor status. Type AB blood, on the other hand, is the universal recipient, as those individuals can receive blood from any type, but they cannot donate universally due to the presence of A and B antigens. Thus, Type O, Rh-negative is the most compatible choice for universal donation.