Oral Iron Repletion Effects On Oxygen Uptake in Heart Failure

Inclusion Criteria: 1. Age \>18 years 2. Previous clinical diagnosis of heart failure with current New York Heart Association (NYHA) Class II-IV symptoms LVEF≤0.40 within 2 years prior to consent, and ≥3 months after a major change in cardiac status (i.e. CABG or CRT). 3. Serum ferritin between 15-100 ng/ml or serum ferritin between 100-299 ng/ml with transferrin saturation \<20% 4. Hemoglobin 9.0-13.5 g/dL (males), 9-13.5 (females) at time of enrollment 5. Stable evidence-based medical therapy for HF (including beta-blocker and ACE-inhibitor/ARB unless previously deemed intolerant, and diuretics as necessary) with \</= 100% change in dose for 30 days prior to randomization a. Changes in diuretic dose guided by a patient-directed flexible dosing program are considered stable medical therapy 6. Willingness to provide informed consent Exclusion Criteria: 1. Presence of a neuromuscular, orthopedic or other non-cardiac condition that prevents the patient from exercise testing on a bicycle/treadmill ergometer and/or inability to achieve an RER ≥ 1.0 on screening/baseline CPET 2. Severe renal dysfunction (eGFR\< 20 ml/min/1.73m2) 3. Severe liver disease (ALT or AST \> 3x normal, alkaline phosphatase or bilirubin \>2x normal) 4. Gastrointestinal conditions known to impair Fe absorption (i.e. inflammatory bowel disease) 5. Known active infection as defined by current use of oral or intravenous antimicrobial agents 6. Documented active gastrointestinal bleeding 7. Active malignancy other than non-melanoma skin cancers 8. Anemia with known cause other than Fe deficiency or chronic disease 9. Fe overload disorders (i.e. hemochromatosis or hemosiderosis) 10. History of erythropoietin, IV or oral Fe therapy, or blood transfusion in previous 3 months. 11. Current ventricular assist device 12. Anticipated cardiac transplantation within the next 4 months 13. Primary hypertrophic cardiomyopathy, infiltrative cardiomyopathy, acute myocarditis, constrictive pericarditis or tamponade 14. Previous adverse reaction to study drug or other oral Fe preparation 15. Known or anticipated pregnancy in the next 4 months