What is the recommended oral iron dosage in mg of elemental iron per day for adults with iron deficiency anemia?

Oral Adult Dosage of Iron for Iron Deficiency Anemia

The recommended oral iron dosage for adults with iron deficiency anemia is 50-100 mg of elemental iron once daily, which is not weight-based but rather a standard dosing approach for all adults. 1, 2

Standard Iron Preparations and Their Elemental Iron Content

• Ferrous sulfate 200 mg tablet = 65 mg elemental iron 1, 3
• Ferrous fumarate 322 mg tablet = 106 mg elemental iron 1, 4
• Ferrous gluconate 300 mg tablet = 37 mg elemental iron 1, 2

Optimal Dosing Strategy

• Once-daily dosing is preferred over multiple daily doses, despite some drug labels recommending 2-3 times daily administration 4, 3
• Morning administration on an empty stomach maximizes absorption 4, 5
• Taking iron with vitamin C (250-500mg) enhances absorption 4
• Alternate-day dosing may be considered if daily dosing causes intolerable side effects, as it can lead to significantly increased fractional iron absorption 6

Monitoring and Treatment Duration

• Monitor hemoglobin response within 2-4 weeks of starting therapy 1, 2
• An absence of hemoglobin rise of at least 10 g/L after 2 weeks predicts treatment failure (sensitivity 90.1%, specificity 79.3%) 1, 2
• Continue treatment for approximately 3 months after hemoglobin normalization to replenish iron stores 1, 2
• After treatment completion, monitor blood counts periodically (every 6 months initially) to detect recurrent anemia 1, 2

Special Considerations

• If standard doses are not tolerated, consider:
  • Reducing the dose to one tablet every other day 2, 6
  • Taking iron with food (though this reduces absorption by up to 50%) 2
  • Switching to an alternative iron formulation 4, 2
• Parenteral iron should be considered when:
  • Oral iron is not tolerated despite modifications 1, 4
  • Oral iron is ineffective (no appropriate hemoglobin response) 1, 5
  • Patient has conditions where oral iron absorption is impaired (e.g., inflammatory bowel disease, post-bariatric surgery) 4, 7

Common Pitfalls to Avoid

• Prescribing multiple daily doses of iron, which increases side effects without improving absorption 4, 6
• Taking iron with tea, coffee, or calcium-containing foods, which inhibit absorption 4
• Using modified-release preparations, which have reduced absorption 1, 4
• Using multivitamin preparations as the sole source of iron supplementation, as they typically contain insufficient elemental iron 4
• Failure to continue treatment after hemoglobin normalization, resulting in inadequate replenishment of iron stores 1, 2