Iron Repletion in Cystic Fibrosis

Participants with cystic fibrosis (CF) will be enrolled in this study. Approximately 80 participants will be enrolled in the Iron Deficient (ID) Cohort; and approximately 20 participants will be enrolled in the Borderline ID Cohort. Participants enrolled in the ID Cohort will be randomized to either an IV versus PO route of iron repletion. Participants enrolled in the Borderline ID Cohort will be randomized to a PO route of iron repletion versus usual care without specific assignment of iron repletion. The focus of the study is the ID Cohort; the Borderline ID Cohort is exploratory.