Observational studies suggest that, compared to patients with chronic kidney disease whose haemoglobin (Hb) levels are on average 11 g/dL, CKD patients with Hb levels < 11 g/dL experience a 20-70% higher risk of death and a 20-40% higher risk of hospitalization [2] and CKD patients with Hb levels > 12 g/dL have a 15-20% lower risk of hospitalization with no survival advantage [3]. This evidence concerns the gene GSTM1 and chronic kidney disease.