In a previous study that compared the effects of oral sodium ferrous citrate versus intravenous saccharated ferric oxide on FGF23 levels in hemodialysis patients with iron deficiency, serum phosphorus levels did not change during the study, whereas iFGF23 levels increased in the intravenous iron group but did not change in the oral iron group; cFGF23 levels decreased in both groups [34]. Here, FGF23 is linked to nutritional disorder.