Sex-specific preoperative haemoglobin levels and the need for perioperative red cell transfusion in men and women are still debated. Cavalli and colleagues examined the appropriateness of World Health Organization (WHO) anaemia thresholds (haemoglobin <130 g L^-1 for males and <120 g L^-1 for females) in a retrospective cohort analysis of >6000 adult patients undergoing cardiac surgery with cardiopulmonary bypass. The authors concluded that the WHO anaemia threshold disproportionately disadvantages female cardiac surgery patients, and a preoperative haemoglobin level of at least 130 g L^-1 should be targeted in all cardiac surgical patients regardless of sex.