The severity of both the serum and bone marrow iron debts observed in these trials led us to investigate alternative dosing schemes that deliver larger quantities of bioavailable iron safely. Ferric carboxymaltose (FCM) is a novel iron-containing complex that allows for the administration of a large replenishment dose of iron (up to 750 mg) over a short infusion period. Several pharmacodynamic properties of FCM render it appealing for use in the treatment of functional iron deficiency associated with surgical critical illness, including a short infusion time, a controlled, sustained delivery of iron to target tissues over a relatively long period of time (up to one week), and minimal hypersensitivity reactions. Increased efficacy and comparable safety have been reported for FCM as compared to iron sucrose for treatment of outpatients with iron-deficiency anemia. There are currently no data regarding the efficacy of FCM for the indication of functional iron deficiency associated with surgical critical illness.