Appropriate Dosing of Iron for Iron Deficiency Anemia
For patients with iron deficiency anemia, oral iron should be administered as 200 mg of elemental iron daily in 2-3 divided doses for adults, or as a single daily dose of ferrous sulfate 200 mg (providing 65 mg elemental iron) with vitamin C to enhance absorption. 1, 2
Oral Iron Therapy
Recommended Dosing
- Adult dosing: 200 mg elemental iron daily, divided into 2-3 doses 1
- Pediatric dosing: 2-3 mg/kg/day of elemental iron 1
- Alternative approach: Single daily dose of ferrous sulfate 200 mg (providing 65 mg elemental iron) 1, 2
- Duration: Continue for 3 months after hemoglobin normalization to replenish iron stores 1, 2
Iron Formulations
- Preferred formulation: Ferrous sulfate (least expensive, 65 mg elemental iron per 325 mg tablet) 1
- Alternatives if not tolerated:
- Ferrous fumarate (108 mg elemental iron per 325 mg tablet)
- Ferrous gluconate (35 mg elemental iron per 325 mg tablet) 1
Administration Tips
- Take iron on an empty stomach (2 hours before or 1 hour after meals) for optimal absorption 1
- Consider once-daily or alternate-day dosing if GI side effects occur 1, 3
- Add vitamin C (250-500 mg) with iron to enhance absorption 1
- Avoid taking with foods, calcium, or aluminum-based phosphate binders 1
Intravenous Iron Therapy
Indications for IV Iron
- Intolerance to oral iron despite trials of different formulations
- Failure to respond to adequate oral iron therapy
- Need for rapid correction of anemia (Hb < 10 g/dL)
- Conditions with impaired oral iron absorption (IBD, bariatric surgery)
- Active inflammatory conditions 1, 2
IV Iron Dosing
For ferric carboxymaltose (preferred IV formulation) 2, 4:
- Patients ≥50 kg: 750 mg IV in two doses separated by at least 7 days (total 1,500 mg)
- Patients <50 kg: 15 mg/kg IV in two doses separated by at least 7 days
- Alternative single-dose option: 15 mg/kg up to maximum 1,000 mg as a single dose 4
Weight-based dosing for IV iron 2:
| Hemoglobin g/dL | Body weight <70 kg | Body weight ≥70 kg |
|---|---|---|
| 10-12 [women] | 1000 mg | 1500 mg |
| 10-13 [men] | 1500 mg | 1500 mg |
| 7-10 | 1500 mg | 2000 mg |
Monitoring and Follow-up
- Check hemoglobin after 2-4 weeks of treatment (expect ~2 g/dL increase)
- Monitor hemoglobin and red cell indices every 3 months for 1 year, then after another year 1, 2
- Target values:
- Hemoglobin >12 g/dL for women, >13 g/dL for men
- Ferritin >100 μg/L
- Transferrin saturation >20% 2
Common Pitfalls to Avoid
- Stopping treatment too early before iron stores are replenished
- Using divided doses when a single daily dose may be better tolerated 1, 3
- Failing to add vitamin C to enhance absorption
- Administering oral iron with absorption inhibitors
- Using parenteral iron when oral therapy would be effective 2
- Inadequate dosing that underestimates total iron deficit 2
Special Considerations
- For patients with chronic kidney disease, oral iron may be less effective; consider IV iron if serum ferritin is >100 ng/mL 1
- For patients with inflammatory bowel disease or after bariatric surgery, IV iron is preferred 1, 2
- Recent research suggests alternate-day dosing may improve absorption and reduce side effects 3