Guidelines developed by the WHO encourage the conservative use of blood in children, restricting routine transfusion to those with severe anaemia, defined as an Hb <40 g/l, or 40–60 g/l with clinical signs of severity.4 However, the underpinning evidence base for this recommendation is weak5 and adherence to these guidelines is poor,6,7 which is compounded by inconsistent Hb threshold recommendations for transfusion for malaria. The gene discussed is GSTM1; the disease is anemia.