Ferrous Fumarate Dosing for Anemia
For adults with iron deficiency anemia, take one 325 mg ferrous fumarate tablet daily (providing 108 mg elemental iron), which is sufficient for most patients and maximizes absorption while minimizing side effects. 1, 2
Standard Adult Dosing
One 325 mg ferrous fumarate tablet daily provides 108 mg of elemental iron, which meets the recommended target of 100-200 mg elemental iron per day for treating anemia 1
The FDA-approved dosing is one tablet daily or as directed by a physician 2
For patients requiring higher doses due to severe anemia or symptoms, two tablets daily (210 mg ferrous fumarate = 216 mg elemental iron) can be given, particularly in menstruating women of reproductive age 1
Optimal Dosing Schedule
Take ferrous fumarate on alternate days rather than daily if using doses ≥60 mg elemental iron, as this maximizes fractional iron absorption by allowing hepcidin levels to subside between doses 3
A recent randomized controlled trial demonstrated that thrice-weekly dosing (200 mg ferrous fumarate three times per week) was non-inferior to thrice-daily dosing for treating iron deficiency anemia, with response rates of 88.9% vs 88.5% at 12 weeks 4
Alternate-day dosing causes fewer gastrointestinal side effects and improves compliance while maintaining efficacy 3, 4
Administration Guidelines
Take on an empty stomach (1 hour before or 2 hours after meals) to maximize absorption, though taking with food is acceptable if gastrointestinal side effects occur 1
Take with vitamin C or citrus juice to enhance iron absorption 1
Separate from calcium supplements by 1-2 hours to avoid interference with absorption 1
Avoid tea and coffee within 1 hour of taking iron, as they inhibit absorption 5
Pediatric Dosing
Children require 2-3 mg/kg/day of elemental iron in divided doses 1
- Liquid iron preparations may be more appropriate for young children than tablets 1
Duration of Treatment
Continue treatment for 3 months after hemoglobin normalizes to adequately replenish iron stores 6
Expect hemoglobin to increase by approximately 1-2 g/dL within 2-4 weeks of starting therapy 6, 5
If no improvement occurs within this timeframe, check adherence first before switching formulations 5
When to Adjust or Switch
If gastrointestinal side effects occur with standard dosing:
- Reduce to alternate-day dosing (one tablet every other day) 7, 3
- Try taking with meals despite reduced absorption 5
- Switch to ferrous sulfate or ferrous gluconate if ferrous fumarate is not tolerated 5
When to Consider IV Iron
Switch to intravenous iron if:
- Oral iron is not tolerated despite trying at least two different formulations 5
- No improvement in blood counts or iron stores after adequate trial of oral supplementation 5
- Severe anemia requiring rapid correction 6
- Malabsorption conditions present 7
Common Pitfalls to Avoid
- Do not prescribe more than once daily dosing routinely, as hepcidin elevation blocks further absorption for up to 48 hours after a single dose 5
- Do not assume treatment failure without checking adherence first 5
- Do not give afternoon or evening doses after a morning dose, as circadian hepcidin increases reduce absorption 3