What are the recommended doses and duration of treatment for iron deficiency anemia?

Recommended Doses and Duration for Iron Deficiency Anemia

For adults with iron deficiency anemia, prescribe 50-100 mg of elemental iron once daily (e.g., one ferrous sulfate 200 mg tablet containing 65 mg elemental iron) taken on an empty stomach, and continue treatment for 2-3 months after hemoglobin normalizes to replenish iron stores. 1

Oral Iron Dosing by Population

Non-Pregnant Adults and Adolescents

• Dose: 60-120 mg elemental iron daily 1
• Optimal regimen: 50-100 mg elemental iron once daily, preferably in the morning on an empty stomach 1
• Alternative: Every-other-day dosing with 60-120 mg may improve tolerance with similar absorption 1, 2
• Duration after Hb normalization: Continue for 2-3 months to replenish iron stores 1

The British Society of Gastroenterology (2021) recommends once-daily dosing as the best compromise based on recent evidence showing that doses ≥60 mg stimulate hepcidin elevation that persists 24 hours, reducing absorption of subsequent doses 1. This represents a shift from older recommendations of divided daily dosing.

Pregnant Women

• Prevention dose: 30 mg/day starting at first prenatal visit 1
• Treatment dose for anemia: 60-120 mg/day 1
• After Hb normalizes: Reduce to 30 mg/day maintenance 1
• Duration: Continue throughout pregnancy 1

Children and Infants

The provided evidence focuses primarily on adults; pediatric dosing should follow age-specific guidelines not detailed in these sources.

Monitoring Response

Initial Assessment

• Check hemoglobin at 2 weeks: Absence of ≥10 g/L rise strongly predicts treatment failure (90% sensitivity, 79% specificity) 1
• Check hemoglobin at 4 weeks: Expect ≥1 g/dL increase in Hb or ≥3% increase in Hct 1
• Ongoing monitoring: Every 4 weeks until Hb normalizes 1

After Normalization

• 3-monthly for 1 year, then 6-monthly for 2-3 years 1
• Restart iron if Hb or MCV falls below normal 1

Enhancing Absorption

Add vitamin C (250-500 mg) with iron doses to enhance absorption 1. The AGA recommends this practice, though the 2011 British guidelines note limited data on effectiveness 1.

When to Use Intravenous Iron

Switch to IV iron if: 1

• Patient cannot tolerate at least two different oral preparations
• No response after 4 weeks of compliant oral therapy 1
• Malabsorption conditions present (inflammatory bowel disease, celiac disease, post-bariatric surgery) 1
• Ongoing blood loss exceeds oral replacement capacity 1

Preferred IV formulations: Those allowing total dose replacement in 1-2 infusions (ferric carboxymaltose, ferric derisomaltose) rather than multiple small doses 1

Common Pitfalls to Avoid

• Don't use divided daily dosing: Recent evidence shows once-daily or alternate-day dosing maximizes absorption and reduces side effects 1, 2
• Don't give afternoon/evening doses after morning dose: Circadian hepcidin increase is augmented by morning iron, blocking subsequent absorption 2
• Don't stop too early: Continue 2-3 months after Hb normalizes to replenish stores; premature discontinuation leads to recurrence 1
• Don't switch between oral iron salts for intolerance: No evidence supports this common practice; consider alternate-day dosing, lower doses, or IV iron instead 1
• Don't use modified-release preparations: These are less suitable for prescribing per British guidelines 1

Formulation Selection

Ferrous sulfate is preferred as the least expensive option with equivalent efficacy to other oral iron salts 1, 3. A standard 200 mg ferrous sulfate tablet contains 65 mg elemental iron 1. Other ferrous salts (fumarate, gluconate) are equally effective but offer no advantage 1.

For patients intolerant to traditional iron salts, ferric maltol (30 mg twice daily) is an alternative, though considerably more expensive 1.