The main objective of this study is to demonstrate the efficacy and safety of an investigational intravenous (IV) iron, ferric carboxymaltose (FCM), compared to oral iron in subjects who have iron deficiency anemia (IDA) and have shown an unsatisfactory response to oral iron.

Inclusion Criteria:

• Male or female subjects ≥ to 18 years of age and able to give informed consent.
• Diagnosis of Iron Deficiency Anemia (IDA).
• Hemoglobin (Hgb) ≤ to 11 g/dL.
• Ferritin ≤ to 100 ng/mL or ≤ 300 when Transferrin Saturation (TSAT) was ≤ 30%.
• Must demonstrate an unsatisfactory response or intolerance to oral iron.

Exclusion Criteria:

• Known hypersensitivity reaction to any component of ferric carboxymaltose or ferrous sulfate.
• Previously randomized in a clinical study of Ferric Carboxymaltose (FCM).
• Requires dialysis for treatment of chronic kidney disease.
• No evidence of iron deficiency.
• Any non-viral infection.
• AST or ALT at screen 1, as determined by central labs, greater than 1.5 times the upper limit of normal.
• Known positive hepatitis with evidence of active disease.
• Received an investigational drug within 30 days of screening.
• Alcohol or drug abuse within the past 6 months.
• Hemochromatosis or other iron storage disorders.
• Estimated life expectancy of less than 6 months or, for cancer patients, an ECOG Performance Status greater than 1.
• Any other laboratory abnormality, medical condition, or psychiatric disorders which in the opinion of the investigator would put the subject's disease management at risk or may result in the subject being unable to comply with study requirements.
• Pregnant or sexually-active females who are of childbearing potential and who are not willing to use an acceptable form of contraception.