Blood Donation Compatibility Calculator

Red blood cells carry antigens (A, B, and RhD), while plasma carries the antibodies against the antigens a person lacks. For red cells, a donor is compatible when they introduce no antigen the recipient has antibodies against. For plasma the logic reverses: the donor's plasma must not contain antibodies against the recipient's red cells. That is why the two comparisons can give opposite answers for the same pair of ABO groups.

O negative red cells carry no A, B, or RhD antigens, so under standard rules there is nothing for a recipient's ABO or anti-D antibodies to react against. This is specific to red cells; O negative plasma is not universal, because it contains both anti-A and anti-B antibodies.

Type AB plasma contains neither anti-A nor anti-B antibodies, so in this standard ABO comparison it can be given to type O, A, B, and AB recipients. This is the plasma counterpart to O negative red cells, and it is why “universal” means different things for red cells and plasma.

A compatible result means two types can be matched in principle under standard rules. It does not mean a specific unit is safe to transfuse, or that a person is eligible to donate. Real transfusions depend on antibody screening, crossmatching, product-specific rules, and clinical judgment, and donation eligibility depends on separate health and safety screening.

For the complete reference matrix, use the blood type compatibility chart.