Ferrous Fumarate Dosage for Iron Deficiency Anemia
The recommended initial dose of ferrous fumarate is one tablet (200 mg, providing approximately 65-108 mg elemental iron) once daily, or if not tolerated, one tablet every other day. 1
Standard Dosing Recommendations
First-Line Oral Therapy
- Start with ferrous fumarate 200 mg (approximately 65-108 mg elemental iron) once daily 1
- This lower, less frequent dosing is based on recent evidence showing that once-daily administration may be equally effective as traditional split-dose regimens while causing fewer adverse effects 1
- Each 325 mg tablet of ferrous fumarate contains approximately 108 mg of elemental iron 1
Alternative Dosing for Intolerance
- If gastrointestinal side effects occur, reduce to one tablet every other day 1
- Alternate-day dosing significantly increases fractional iron absorption in iron-depleted individuals and reduces adverse effects 1
- This approach is supported by data showing that hepcidin elevation from daily dosing can reduce subsequent iron absorption by 35-45% 1
Traditional Higher-Dose Regimens (Less Preferred)
- Older guidelines recommended 200 mg elemental iron daily in 2-3 divided doses 1
- For severe anemia or symptomatic patients, some sources suggest 200 mg elemental iron per day (approximately two 200 mg ferrous fumarate tablets) 2
- However, the traditional dosing of 200 mg ferrous fumarate three times daily is based on poor-quality evidence and is no longer recommended as first-line 2
Key Dosing Principles
Absorption Optimization
- Take iron on an empty stomach for maximum absorption 1
- Avoid tea, coffee, milk, or antacids within one hour of iron administration, as these significantly inhibit absorption 1, 3
- Consider adding ascorbic acid 250-500 mg twice daily to enhance absorption, though clinical evidence is limited 3
Monitoring Response
- Check hemoglobin after 2-4 weeks: expect at least 1.0 g/dL increase 1, 3
- Continue treatment for approximately 3 months after hemoglobin normalization to replenish iron stores 1
- If ferritin does not increase within one month in adherent patients, consider switching to intravenous iron 1
When to Consider Intravenous Iron Instead
Switch to IV iron if:
- Oral iron is not tolerated despite dose reduction 1
- No hemoglobin response after 2-4 weeks of adequate oral therapy 1, 3
- Malabsorption conditions present (post-bariatric surgery, active inflammatory bowel disease) 1
- Severe anemia requiring rapid correction 3, 2
IV Iron Options
- Iron sucrose 200 mg weekly 1, 3
- Ferric carboxymaltose 750-1000 mg (1-2 doses) 1
- Low-molecular-weight iron dextran 1000 mg single dose 1
Important Caveats
Common Pitfalls
- Avoid overprescribing: The traditional three-times-daily dosing causes more side effects without proven additional benefit 1, 2
- Don't defer treatment: Begin iron replacement immediately; don't wait for diagnostic workup unless colonoscopy is imminent 1
- Monitor for non-response: Failure to respond suggests either non-compliance, ongoing blood loss, malabsorption, or inflammatory conditions blocking iron utilization 1
Special Populations
- In inflammatory bowel disease, oral ferrous fumarate may worsen clinical disease activity; strongly consider IV iron as first-line in active IBD 4
- In chronic kidney disease patients, 200 mg elemental iron daily in divided doses may be needed 1
- Elderly patients may require prolonged treatment (6 months) at 5 mg/kg/day elemental iron for optimal response 5