What is the recommended dose and frequency of ferric sulfate (iron supplement) for treating iron deficiency anemia?

Ferrous Sulfate Dosing for Iron Deficiency Anemia

For iron deficiency anemia, give ferrous sulfate 200 mg (65 mg elemental iron) once daily, taken in the morning on an empty stomach, and continue for 3 months after hemoglobin normalizes to replenish iron stores. 1

Optimal Dosing Strategy

Once daily dosing is superior to divided doses:

• A single daily dose of 50-100 mg elemental iron (e.g., one ferrous sulfate 200 mg tablet) taken in the fasting state is the best compromise for initial treatment 1
• Oral iron doses ≥60 mg stimulate hepcidin elevation that persists for 24 hours, reducing absorption of subsequent doses 2
• Once daily dosing achieves similar hemoglobin response as twice or three times daily dosing, with better tolerability 1, 3

Alternate-day dosing may be even better:

• Alternate day administration of 100-200 mg elemental iron significantly increases fractional iron absorption compared to daily dosing 1
• The hepcidin response subsides by 48 hours, allowing improved absorption with alternate-day schedules 2
• Alternate-day dosing reduces gastrointestinal side effects (relative risk 0.56 for GI adverse events) 1
• If rapid hemoglobin response is critical, give twice the target daily dose on alternate days to maximize total iron absorption 2

Timing and Administration

• Take in the morning on an empty stomach - the circadian increase in hepcidin is augmented by morning iron doses, so avoid afternoon or evening dosing 2
• Ascorbic acid 250-500 mg may enhance absorption, though evidence for clinical effectiveness is limited 1

Duration of Treatment

• Monitor hemoglobin response at 4 weeks - failure to achieve at least 10 g/L rise after 2 weeks predicts subsequent treatment failure (sensitivity 90.1%, specificity 79.3%) 1
• Continue for 3 months after hemoglobin normalizes to adequately replenish iron stores 1
• Monitor blood counts every 4 weeks until hemoglobin normalizes 1

Special Populations

For inflammatory bowel disease patients:

• Limit to maximum 100 mg elemental iron per day 1
• Use only in mild anemia (Hb 11.0-12.9 g/dL in men, 11.0-11.9 g/dL in women) with clinically inactive disease 1
• Consider intravenous iron as first-line if disease is active, hemoglobin <10 g/dL, or previous oral iron intolerance 1

When Oral Iron Fails

Consider parenteral iron when:

• Oral iron is contraindicated, ineffective, or not tolerated 1
• Chronic disease, continuing blood loss, impaired absorption, or GI inflammatory pathology is present 1
• No hemoglobin response after 4 weeks of adequate oral therapy 1

Common Pitfalls to Avoid

• Don't prescribe divided daily doses - this reduces absorption due to hepcidin elevation and increases side effects 1, 2
• Don't switch between different ferrous salts for intolerance - this practice is not supported by evidence; instead consider ferric maltol, alternate-day dosing, or parenteral iron 1
• Don't stop too early - continue for 3 months after hemoglobin normalizes, not just until anemia resolves 1
• Don't use high-molecular weight ferric preparations orally - ferrous iron is absorbed 4-10 times better than ferric iron 4

Long-term Monitoring

• Check blood counts every 3 months for the first year after treatment completion 1
• Then recheck at 1 year, and subsequently only if symptoms recur 1
• Recurrent anemia warrants further investigation 1