An expert consensus of different Spanish scientific societies addresses the management of anaemia in surgical procedures with medium-high bleeding, such as CRC surgery, and advises that it would be desirable to reach haemoglobin (Hb) levels > 13 g/dL before surgery in order to minimise the risk of transfusion and quickly correct the anaemia [10, 12]. The gene discussed is GSTM1; the disease is anemia (phenotype).