Blood transfusion safety comes down to a simple antigen rule: a recipient can only receive red blood cells from a donor whose antigens the recipient already carries. This reference computes compatibility for all 8 ABO/Rh blood groups from first principles rather than reciting a fixed chart, and shows the full transfusion matrix at a glance.
How it works
Each red blood cell can carry up to three antigens that matter here: A, B (the ABO system) and RhD (the Rhesus D antigen, which makes a type “positive”). Your immune system makes antibodies against any ABO antigen you do not have, so transfusing cells with a foreign antigen triggers a reaction.
The compatibility rule is therefore: a donor’s red cells are safe for a recipient if every antigen the donor carries is also present on the recipient. The tool derives each type’s antigens (for example AB+ has A, B and RhD; O- has none) and applies this check across all pairs. Because O- carries no antigens it can give to anyone, and because AB+ carries all three it can receive from anyone.
Reading the matrix and notes
The matrix lists each recipient alongside the donor types whose red cells they can safely accept. Use the direction switch to flip between donating and receiving from the perspective of one selected type. Rh-negative recipients are deliberately restricted to Rh-negative donors to avoid anti-D sensitisation, which is particularly important in pregnancy.
This tool models red-cell (RBC) transfusion only; plasma compatibility runs in the opposite direction. It is an educational reference and not a substitute for crossmatching and antibody screening performed by a qualified blood bank.