Issues surrounding iron supplementation of critically ill patients include formulation, dose, route of administration, hepcidin antagonism, and mitigation of the complications of iron overload, particularly infection. Our first RCT of iron supplementation of critically ill surgical patients compared enteral ferrous sulfate 325 mg thrice daily to placebo (NCT00450177). Although a significant reduction in pRBCs transfusion requirement for the iron group was observed, low injury severity, intolerance of enteral medications, and a predominance of traumatic brain injury limited generalizability. In a second multicenter RCT, we compared intravenous iron sucrose 100 mg thrice weekly to placebo among critically ill trauma patients (NCT01180894, NTI-ICU-008-01) [8]. Iron supplementation using this generic dosing scheme did not impact the serum iron concentration, TSAT, IDE, anemia, or pRBCs transfusion requirement. Rather, iron supplementation accumulated as ferritin as evidenced by a significantly increased serum ferritin concentration in the iron as compared to the placebo group at all time points. Iron supplementation did not increase the risk of infection in either trial, despite a relatively high incidence of marked hyperferritinemia (serum ferritin concentration > 1,000 ng/mL) in the iron group.