What is the best oral iron replacement for iron deficiency?

Best Oral Iron Replacement for Iron Deficiency

Ferrous sulfate 200 mg once daily (65 mg elemental iron) is the best oral iron replacement for iron deficiency due to its proven efficacy, safety, and cost-effectiveness. 1

First-Line Treatment Options

• Ferrous sulfate is the most cost-effective iron formulation, with no single formulation having proven advantages over others in terms of tolerability 2
• Standard ferrous sulfate tablets (200 mg) provide 65 mg of elemental iron per tablet and cost approximately £1.00 for a 28-day supply, making them significantly less expensive than other formulations 3
• Alternative ferrous salts can be considered if ferrous sulfate is not tolerated:
  • Ferrous fumarate (provides 69-106 mg elemental iron per tablet)
  • Ferrous gluconate (provides 37 mg elemental iron per tablet) 1

Optimal Dosing Strategy

• Once-daily dosing of 50-100 mg elemental iron is recommended rather than multiple daily doses 3, 1
• Taking iron on an empty stomach maximizes absorption, though this may increase gastrointestinal side effects 1
• Recent evidence suggests alternate-day dosing may improve fractional iron absorption and reduce side effects 4
• The absence of a hemoglobin rise of at least 10 g/L after 2 weeks of daily oral iron therapy strongly predicts subsequent treatment failure (sensitivity 90.1%, specificity 79.3%) 3

Strategies to Improve Absorption and Tolerability

• Taking iron with vitamin C (250-500mg) enhances absorption by forming a chelate with iron 2, 1
• Avoid taking iron with tea or coffee, which inhibit absorption 2, 1
• If standard doses are not tolerated, consider:
  • Reduced dose
  • Taking with food (though this may slightly decrease absorption)
  • Switching to an alternative iron formulation 1
• Common side effects include constipation (12%), diarrhea (8%), and nausea (11%) 1

Special Considerations

• Modified-release preparations are indicated as "less suitable for prescribing" according to the British National Formulary 3
• Ferric maltol may be considered for patients with previous intolerance to traditional iron salts, though it is considerably more expensive (£47.60 vs £1.00 for a 28-day supply of ferrous sulfate) 3, 1
• Avoid multivitamin preparations as the sole source of iron supplementation as they typically contain insufficient elemental iron (up to 14 mg) for treating iron deficiency anemia 3, 1

When to Consider Parenteral Iron

• Intravenous iron should be considered when:
  • Oral iron is not tolerated despite modifications
  • Ferritin levels do not improve with oral iron trial
  • Patient has conditions where oral iron absorption is impaired (e.g., inflammatory bowel disease, post-bariatric surgery) 2
• Parenteral iron can produce a clinically meaningful hemoglobin response within a week and should be considered as an alternative to blood transfusion in most cases 3

Monitoring Response

• Monitor hemoglobin response within the first 4 weeks of treatment 1
• Expect hemoglobin to increase by approximately 1 g/dL within 2 weeks in patients responding to therapy 2, 1
• Treatment should be continued for approximately 3 months after hemoglobin normalizes to ensure adequate repletion of marrow iron stores 1