The Iron and Heart trial showed that in non-anaemic adults with stage 3b–5 CKD and iron deficiency, not receiving dialysis, IV iron maintained a stable Hb concentration at months 1 and 3 (n = 26) compared with placebo (n = 28). A modest, numerical improvement in QoL and functional capacity was observed. The gene discussed is GSTM1; the disease is chronic kidney disease.