Group I (treatment group): Subjects assigned to this group will receive intravenous iron (ferric sucrose product Venofer® 2%, 5mL/ampoule) in a starting dose of 200mg (2 ampoules) diluted in 150mL 0.9% NaCl solution, over 60 minutes, once a week for the first four administrations, and then every other week until hemoglobin levels reach 12g/dL. Then, iron dose will be adjusted to 1 ampoule at 2-4 weeks interval, as needed to maintain these levels with serum ferritin ≤500ng/mL.