Recommended Dosage of Ferrous Sulfate for Iron Deficiency
The recommended first-line treatment for iron deficiency is ferrous sulfate 50-100 mg of elemental iron once daily, taken in the morning on an empty stomach, continued for 3 months after hemoglobin normalization. 1
Dosing Guidelines
Standard Dosing
- Each ferrous sulfate tablet typically contains 324 mg of ferrous sulfate, equivalent to 65 mg of elemental iron 2
- For adults with iron deficiency:
- 200 mg of elemental iron per day, in 2-3 divided doses 3
- Alternatively, 50-100 mg of elemental iron once daily in the morning on an empty stomach 1
- For women of reproductive age who are menstruating: additional requirements of 50-100 mg elemental iron daily (equivalent to two 200-mg ferrous sulfate tablets daily) 3
Population-Specific Dosing
| Population | Daily Elemental Iron Intake |
|---|---|
| Nonpregnant women and adolescent girls | 60-120 mg |
| School-age children | 60 mg |
| Adolescent boys | 120 mg |
| Pregnant women (prevention) | 30 mg |
| Pregnant women (treatment) | 60-120 mg |
Optimizing Absorption
Timing and Administration
- Take on an empty stomach in the morning 1
- Taking with 500 mg vitamin C (ascorbic acid) enhances absorption 1
- Avoid taking with:
- Tea or coffee (wait at least 1 hour after iron intake)
- Calcium supplements
- High-fiber foods 1
Alternate-Day Dosing
- Recent evidence suggests alternate-day dosing may improve absorption and reduce side effects 4
- For iron-deficient women, doses ≥60 mg stimulate hepcidin increase that persists 24 hours but subsides by 48 hours 4
- Morning doses are preferred over afternoon/evening doses due to circadian hepcidin patterns 4
Duration of Treatment
- Continue treatment for 3 months after hemoglobin normalizes to replenish iron stores 1
- Monitor hemoglobin response within the first 4 weeks of starting therapy 1
- Target ferritin >100 μg/L to ensure adequate iron stores are replenished 1
Alternative Formulations
- If ferrous sulfate is not tolerated:
Monitoring
- Check hemoglobin within 4 weeks of starting therapy 1
- Monitor blood count periodically (every 6 months initially) 1
- Ferritin interpretation:
- <30 μg/L: Definitive iron deficiency
- 30-100 μg/L with transferrin saturation <20%: Possible iron deficiency
100 μg/L with normal transferrin saturation: Iron deficiency unlikely 1
Common Pitfalls to Avoid
- Discontinuing therapy too early (before 3 months after hemoglobin normalization) 1
- Prescribing multiple daily doses when single morning dose may be more effective 1, 4
- Using modified-release preparations which have reduced absorption 1
- Overreliance on ferritin alone for diagnosis in inflammatory conditions 1
For patients who cannot tolerate oral iron, have poor absorption, or have ongoing blood loss, intravenous iron should be considered as an alternative treatment approach 1, 5.