Erythrocyte Thomsen-Friedenreich crypt antigen (T-antigen) activation is not an uncommon event in infants with severe necrotising enterocolitis (NEC). Transfusion of these infants with blood products containing plasma carries the risk of causing intravascular haemolysis. T-antigen activation is easily detected using a rapid simple lectin agglutination test. Early recognition of T-antigen activation ensures the correct choice of plasma free transfusion therapy. We describe an infant with severe NEC complicated by T-antigen activation and haemolysis.