Iron Supplementation Guidelines

Introduction to Iron Dosing

• The British Society of Gastroenterology recommends once daily dosing of 50-100 mg elemental iron taken in the fasting state as the best compromise option for initial treatment 2, 3
• Oral doses of 60 mg elemental iron stimulate hepcidin levels, reducing subsequent iron absorption by 35-45%, making the overall absorption from 60 mg once daily similar to 60 mg twice daily 1, 2

Evidence-Based Dosing Recommendations

• The British Society of Gastroenterology (2021) recommends once daily dosing of 50-100 mg elemental iron, which translates to one ferrous sulfate 200 mg tablet (65 mg elemental iron) once daily 1, 2
• For patients with inflammatory bowel disease, no more than 100 mg elemental iron per day is recommended, as unabsorbed iron may exacerbate disease activity 4, 5

Monitoring and Expected Response

• Hemoglobin should rise by at least 10 g/L after 2 weeks of daily oral iron therapy 3
• Treatment should continue for approximately 3 months after hemoglobin normalization to replenish iron stores 1, 2

When Higher or More Frequent Dosing May Be Considered

• If the patient tolerates once-daily dosing well and shows suboptimal response after 2-4 weeks, consider increasing to 325 mg once daily (105 mg elemental iron) 1
• If oral iron is not tolerated, reduce to one tablet every other day rather than increasing frequency 2

Alternative Approaches for Poor Response

• Switch to alternate-day dosing (which paradoxically improves absorption) 1, 2
• Consider ferric maltol (30 mg twice daily) for patients intolerant to traditional iron salts 1, 2
• Intravenous iron should be considered when oral iron is contraindicated, ineffective, or not tolerated 1, 2

Common Pitfalls to Avoid

• Do not assume that doubling the dose doubles the benefit—iron absorption is saturable and hepcidin-regulated 1, 2
• Modified-release preparations (including 325 mg formulations) are less suitable for prescribing as they release iron beyond the duodenum where absorption is optimal 1, 2
• The absence of hemoglobin rise after 2 weeks strongly predicts subsequent treatment failure (sensitivity 90.1%, specificity 79.3%) 3