Treatment of Iron Deficiency Anemia When Oral Iron Is Not Effective
Intravenous iron therapy should be used when oral iron supplementation is not effective in treating iron deficiency anemia with low ferritin levels. 1
When to Consider IV Iron Therapy
Intravenous iron is indicated in the following situations:
- When patients do not tolerate oral iron
- When ferritin levels do not improve with a trial of oral iron
- When the patient has a condition in which oral iron is not likely to be absorbed 1
Specific Indications for IV Iron as First-Line Treatment
- Clinically active inflammatory bowel disease
- Previous intolerance to oral iron
- Hemoglobin below 100 g/L (10 g/dL)
- Patients who need erythropoiesis-stimulating agents 1
- Patients with bariatric procedures, particularly those that disrupt normal duodenal iron absorption 1
- Patients with ongoing bleeding who do not respond to oral iron therapy 1
Dosing of IV Iron
The estimation of iron need is usually based on baseline hemoglobin and body weight:
| Hemoglobin g/L | Body weight <70 kg | Body weight ≥70 kg |
|---|---|---|
| 100-120 (women) or 100-130 (men) | 1000 mg | 1500 mg |
| 70-100 | 1500 mg | 2000 mg |
Choice of IV Iron Formulation
- IV iron formulations that can replace iron deficits with 1 or 2 infusions are preferred over those requiring more than 2 infusions 1
- All IV iron formulations have similar risk profiles; true anaphylaxis is very rare 1
- The vast majority of reactions to IV iron are complement activation-related pseudo-allergy (infusion reactions) 1
- Ferric carboxymaltose has been shown to effectively increase hemoglobin levels and replenish iron stores 2
Monitoring Response to IV Iron Therapy
After successful treatment with IV iron, re-treatment should be initiated as soon as:
- Serum ferritin drops below 100 μg/L, or
- Hemoglobin falls below 120 g/L for women or 130 g/L for men 1
Laboratory monitoring should include:
- Hemoglobin levels (checked after 3-4 weeks to assess response)
- Iron parameters (ferritin, transferrin saturation) after 4-8 weeks of treatment 3
Special Considerations
Inflammatory Conditions
- In patients with inflammatory conditions, ferritin may be falsely elevated despite iron deficiency
- In the presence of inflammation, a serum ferritin up to 100 μg/L may still be consistent with iron deficiency 1
- If ferritin is between 30 and 100 μg/L with inflammation present, a combination of true iron deficiency and anemia of chronic disease is likely 1
Inflammatory Bowel Disease
- Active inflammation should be treated effectively to enhance iron absorption or reduce iron depletion 1
- IV iron therapy should be given in individuals with IBD, iron-deficiency anemia, and active inflammation with compromised absorption 1
- Quality of life improves with correction of anemia, and this improvement is independent of clinical activity 1
Potential Pitfalls
- Failing to investigate the underlying cause of iron deficiency
- Relying solely on hemoglobin response without monitoring iron parameters
- Misinterpreting iron studies during inflammation
- Inadequate duration of treatment leading to incomplete replenishment of iron stores 3
By following these evidence-based recommendations, patients with iron deficiency anemia who do not respond to oral iron therapy can achieve improved hemoglobin levels, replenished iron stores, and better quality of life.