ANATOMY

Detailed explanation-1: -Answer From Rajiv K. Pruthi, M.B.B.S. For emergency transfusions, blood group type O negative blood is the variety of blood that has the lowest risk of causing serious reactions for most people who receive it. Because of this, it’s sometimes called the universal blood donor type.

Detailed explanation-2: -Universal donors are those with an O negative blood type. Why? O negative blood can be used in transfusions for any blood type.

Detailed explanation-3: -O positive red blood cells are not universally compatible to all types, but they are compatible to any red blood cells that are positive (A+, B+, O+, AB+). Over 80% of the population has a positive blood type and can receive O positive blood.

Detailed explanation-4: -Type O blood is called the universal donor because: It has neither A nor B surface antigens on the red blood cells. Antigens are proteins that are capable of evoking an allergic response in someone whose whole body does not have the antigens.

Detailed explanation-5: -Blood group O can be donated to any of the other blood groups as it has no antigens, to initiate an antibody reaction. Thus blood group O is the universal donor.