The rationale to perform this study was based on clinical experience managing 2 cases of symptomatic, severe hypocalcemia that occurred between 7 and 10 d after i.v. iron polymaltose infusion and corresponded with hypophosphatemia, reduced serum calcitriol concentration, and markedly elevated levels of FGF23 (Table 1). Here, FGF23 is linked to Hypocalcemia.