What is the recommended dose of ferrous sulfate (iron supplement) and other ferrous medications for treating iron deficiency?

Recommended Dosing for Iron Deficiency Treatment

For treating iron deficiency anemia, prescribe ferrous sulfate 200 mg (65 mg elemental iron) once daily or every other day, as alternate-day dosing maximizes absorption while minimizing side effects. 1

Optimal Oral Iron Regimen

First-Line Treatment: Ferrous Sulfate

• Ferrous sulfate is the preferred formulation because it is the least expensive option with no therapeutic advantage of other formulations over it 1
• Standard ferrous sulfate 200 mg tablet contains 65 mg elemental iron 1, 2
• Target dose: 50-100 mg elemental iron daily 1

Dosing Frequency: Once Daily or Alternate Days

• Give oral iron once daily at most—more frequent dosing does not improve absorption 1
• Alternate-day dosing (every 48 hours) is equally or more effective than daily dosing because:
  • Oral iron doses ≥60 mg stimulate hepcidin elevation that persists 24 hours, blocking subsequent iron absorption by 35-45% 1, 3
  • Fractional iron absorption is significantly higher with alternate-day administration 1, 3
  • Better tolerability may improve adherence 3
• Administer in the morning only—avoid afternoon/evening doses as circadian hepcidin increases are augmented by morning iron, reducing absorption of later doses 3

Enhancing Absorption

• Add vitamin C (250-500 mg) with each iron dose to enhance absorption 1
• Take on an empty stomach when possible for optimal absorption 1

Alternative Oral Formulations (If Ferrous Sulfate Not Tolerated)

All ferrous salts are equally effective 1:

• Ferrous fumarate: 210-322 mg tablets (69-106 mg elemental iron) 1
• Ferrous gluconate: 300 mg tablets (37 mg elemental iron) 1
• Ferric maltol: 30 mg twice daily—better tolerated in inflammatory bowel disease patients with previous intolerance to ferrous salts, though more expensive 1

Treatment Duration and Monitoring

• Monitor hemoglobin response at 4 weeks—expect 2 g/dL rise by 3-4 weeks 1
• Continue treatment for 3 months after hemoglobin normalization to replenish iron stores 1
• Check blood count every 3 months for the first year, then at 6-12 month intervals 1

When to Use Parenteral Iron Instead

Switch to intravenous iron when: 1

• Oral iron is not tolerated despite trying alternate formulations or reduced dosing
• Ferritin levels fail to improve after adequate trial of oral iron
• Malabsorption conditions present (celiac disease, inflammatory bowel disease, post-bariatric surgery)
• Ongoing significant blood loss
• Severe anemia with hemoglobin <7-10 g/dL requiring rapid correction 1
• Chronic inflammatory conditions (chronic kidney disease, heart failure, active IBD) 1, 4
• Second or third trimester of pregnancy 4

Special Population Considerations

Inflammatory Bowel Disease

• Limit to 100 mg elemental iron daily maximum in IBD patients, as higher doses may exacerbate inflammation 1
• Consider intravenous iron as first-line in active disease 1

Chronic Kidney Disease

• 200 mg elemental iron daily in 2-3 divided doses for CKD patients on peritoneal dialysis 1
• Intravenous iron often preferred in hemodialysis patients 1

Common Pitfalls to Avoid

• Do not prescribe modified-release preparations—they are less suitable as iron is released beyond the duodenum where absorption is optimal 1
• Do not give multiple daily doses—this triggers hepcidin and blocks absorption of subsequent doses 1, 3
• Do not defer iron therapy while awaiting investigations unless colonoscopy is imminent 1
• Do not continue ineffective oral iron indefinitely—if no hemoglobin response by 4 weeks, reassess for compliance, continued blood loss, malabsorption, or switch to parenteral iron 1