What is the recommended treatment for a patient with iron deficiency anemia using oral iron supplementation with elemental iron?

Oral Iron Supplementation for Iron Deficiency Anemia

For adults with iron deficiency anemia, prescribe 50-100 mg of elemental iron once daily, taken in the morning on an empty stomach, and continue treatment for approximately 3 months after hemoglobin normalizes to replenish iron stores. 1

Dosing Strategy

Standard Dosing

• Administer 50-100 mg elemental iron once daily rather than divided doses throughout the day 1
• Doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours, blocking further iron absorption when additional doses are given the same day 1, 2
• Once-daily dosing provides similar total iron absorption to multiple daily doses but with fewer side effects 1

Alternate-Day Dosing Option

• Consider alternate-day dosing (100-200 mg elemental iron every other day) if patients experience gastrointestinal side effects 1
• Fractional iron absorption is significantly higher with alternate-day administration compared to daily dosing 1, 2
• Hepcidin levels subside by 48 hours, allowing improved absorption with the next dose 2
• This approach may improve tolerance while maintaining efficacy 1, 2

Timing and Administration

• Give iron in the morning as a single dose 2
• The circadian increase in hepcidin is augmented by morning iron doses, making afternoon or evening dosing after a morning dose counterproductive 2
• Take on an empty stomach for optimal absorption 1
• Food reduces iron absorption by up to 50% when consumed within 2 hours before or 1 hour after the dose 1

Enhancing Absorption

• Add 80 mg vitamin C (ascorbic acid) to improve iron absorption 1, 2
• Vitamin C forms a chelate with iron preventing insoluble compound formation and reduces ferric to ferrous iron 1
• Avoid tea and coffee within 1 hour of iron intake as they powerfully inhibit absorption 1

Available Formulations

The most common and cost-effective oral iron preparations include 1, 3, 4:

• Ferrous sulfate: 65 mg elemental iron per 200-325 mg tablet (most economical at ~£1.00/28 days)
• Ferrous fumarate: 69-106 mg elemental iron per tablet
• Ferrous gluconate: 37-38 mg elemental iron per tablet
• Ferric maltol: 30 mg elemental iron per tablet (better tolerated in inflammatory bowel disease but more expensive at £47.60/28 days)

Start with ferrous sulfate or ferrous fumarate as they are least expensive and equally effective 1. There is no strong evidence that any oral formulation is superior in efficacy or tolerability 1.

Monitoring and Duration

• Check hemoglobin response within 4 weeks of starting treatment 1
• Hemoglobin should increase by approximately 1 g/dL within 2 weeks in adherent patients 1
• Continue treatment for approximately 3 months after hemoglobin normalizes to ensure adequate replenishment of marrow iron stores 1
• After restoration of hemoglobin and iron stores, monitor blood count every 6 months initially to detect recurrent anemia 1

When to Switch to Intravenous Iron

Consider parenteral iron when oral iron is contraindicated, ineffective, or not tolerated 1. Specific indications include:

• No hemoglobin response after 4 weeks despite compliance and absence of acute illness 1
• Ferritin levels fail to improve after 1 month of adherent oral therapy 1
• Gastrointestinal side effects (constipation 12%, diarrhea 8%, nausea 11%) prevent compliance 1
• Active inflammatory bowel disease with compromised absorption 1
• Post-bariatric surgery with disrupted duodenal absorption 1
• Ongoing blood loss exceeding oral iron replacement capacity 1
• Chronic kidney disease on dialysis 1
• Chronic heart failure (oral iron poorly absorbed due to gut edema and shows no prognostic benefit) 1

Special Populations

Pregnant Women

• Start 30 mg/day elemental iron at first prenatal visit for prevention 1
• Treat anemia with 60-120 mg/day elemental iron 1
• Continue until hemoglobin normalizes for gestational stage, then reduce to 30 mg/day 1

Inflammatory Bowel Disease

• Limit oral iron to ≤100 mg elemental iron daily 1
• Intravenous iron is preferred with active inflammation and hemoglobin <100 g/L 1
• Optimize disease control to enhance iron absorption 1

Chronic Kidney Disease

• Prescribe 200 mg elemental iron daily in 2-3 divided doses for predialysis patients 1
• Pediatric dose: 2-3 mg/kg/day 1
• Intravenous iron required if oral therapy ineffective or dialysis commenced 1

Common Pitfalls

• Avoid enteric-coated or modified-release formulations as they may improve tolerability but significantly decrease absorption 1
• Do not prescribe multiple daily doses—this increases side effects without improving absorption due to hepcidin elevation 1, 2
• Aluminum-based phosphate binders reduce iron absorption; separate administration 1
• Recognize that ferritin up to 100 μg/L may still reflect iron deficiency in inflammatory conditions 1