Instructions for Taking Iron Supplements for Iron Deficiency Anemia
For treating iron deficiency anemia, take 50-100 mg of elemental iron once daily, preferably as ferrous sulfate, on an empty stomach or with vitamin C to enhance absorption, and continue treatment for approximately 3 months after hemoglobin normalizes to replenish iron stores. 1
Optimal Dosing Strategy
Frequency and Timing
- Take iron once daily at most—daily dosing is as effective as multiple doses per day, with better tolerability 1
- Alternate-day dosing (every other day) may be equally or more effective than daily dosing for some patients, as doses ≥60 mg stimulate hepcidin elevation that persists 24 hours and reduces absorption of subsequent doses 1, 2
- Take iron in the morning rather than afternoon or evening, as circadian hepcidin increases are augmented by morning doses 2
Dose Amount
- Standard dose: 50-100 mg elemental iron daily for adults 1
- Higher doses (60-120 mg) may be used for treatment of anemia 1
- Lower doses are often as effective as higher doses and better tolerated 1
- Doses above 60 mg do not significantly increase total iron absorption due to hepcidin-mediated inhibition 1
Iron Formulation Selection
Preferred Formulation
- Ferrous sulfate is the preferred formulation as it is the least expensive and equally effective as other iron preparations 1
- No single oral iron formulation has advantages over others in terms of efficacy 1
- Alternative ferrous salts (ferrous fumarate, ferrous gluconate) are equally effective if ferrous sulfate is not tolerated 1
Elemental Iron Content
Common preparations and their elemental iron content 1:
- Ferrous sulfate 200 mg tablet = 65 mg elemental iron
- Ferrous fumarate 210 mg tablet = 69 mg elemental iron
- Ferrous gluconate 300 mg tablet = 37 mg elemental iron
Enhancing Absorption
- Add vitamin C (250-500 mg) with iron supplementation to improve absorption 1
- Take iron on an empty stomach when possible for optimal absorption 1
- If gastrointestinal side effects occur, taking iron with food may improve tolerance, though this reduces absorption 1
Duration of Treatment
- Continue iron therapy for approximately 3 months after hemoglobin normalizes to ensure adequate replenishment of iron stores 1
- For confirmed iron deficiency anemia, continue treatment for 2-3 additional months after correction 1
- Monitor hemoglobin response within the first 4 weeks of treatment 1
Monitoring Response
Expected Response
- Hemoglobin should increase by approximately 1-2 g/dL after 3-4 weeks of treatment 1
- Reticulocyte count increases within a few days as the earliest sign of response 3
Follow-up Schedule
- Check hemoglobin at 4 weeks to confirm response 1
- After normalization, monitor blood counts every 3 months for the first year, then annually 1
- If no response after 4 weeks despite compliance, further evaluation with additional laboratory tests (MCV, RDW, serum ferritin) is needed 1
When to Consider Intravenous Iron
Switch to intravenous iron if: 1
- Oral iron is not tolerated despite trying at least two different formulations
- Ferritin levels do not improve with adequate trial of oral iron
- Malabsorption conditions are present (celiac disease, inflammatory bowel disease with active inflammation, post-bariatric surgery)
- Oral iron is contraindicated
Common Pitfalls to Avoid
- Avoid taking multiple doses per day—this increases hepcidin and reduces subsequent absorption while increasing side effects 1, 2
- Do not take iron with calcium, antacids, or tea/coffee—these inhibit absorption 1
- Do not stop treatment when hemoglobin normalizes—iron stores require additional months to replenish 1
- Do not assume lack of response means treatment failure—check compliance first, as poor adherence is the most common cause of treatment failure 1
Special Populations
Pregnant Women
- Start with low-dose iron (30 mg/day) at first prenatal visit for prevention 1
- For treatment of anemia during pregnancy, use 60-120 mg/day 1
- Reduce to 30 mg/day maintenance dose once hemoglobin normalizes for gestational stage 1