The importance of adequate iron availability was stressed in the earliest EPO studies in HD patients [12], yet few reports on the effects of EPO and newer ESAs have explicitly addressed the need of patients for adequate iron [2,3,10], and ESA effects have been tested in CKD patients at least 25–30% of whom had evidence of iron deficiency at study start before the ESA was given [2,3,10]. This evidence concerns the gene EPO and nutritional disorder.