When to Order IV Iron for Iron Deficiency Anemia
Order intravenous iron when patients do not tolerate oral iron, fail to improve ferritin levels after a trial of oral iron, or have conditions where oral iron absorption is impaired. 1
General Indications for IV Iron
The 2024 American Gastroenterological Association guidelines provide clear criteria for transitioning from oral to intravenous iron therapy:
Primary Indications
- Oral iron intolerance: Patients experiencing gastrointestinal side effects (nausea, constipation, dyspepsia) that prevent adherence 1, 2
- Failed oral iron trial: Ferritin levels remain low despite adequate oral supplementation 1
- Malabsorption conditions: Any disorder where oral iron is unlikely to be absorbed effectively 1
Specific Clinical Scenarios Requiring IV Iron
Post-bariatric surgery patients with iron deficiency anemia and no identifiable chronic GI blood loss should receive IV iron, particularly after procedures disrupting duodenal iron absorption 1
Inflammatory bowel disease (IBD) patients with active inflammation and compromised absorption require IV iron therapy 1. The key is determining whether anemia stems from inadequate intake/absorption versus iron loss from bleeding 1
Celiac disease patients should first ensure gluten-free diet adherence, then try oral iron based on severity and tolerance, followed by IV iron if stores don't improve 1, 3
Portal hypertensive gastropathy: Start with oral iron initially, but switch to IV iron for ongoing bleeding unresponsive to oral therapy 1
Heart failure with iron deficiency: IV iron is indicated to improve exercise capacity in NYHA class II/III patients, with specific dosing based on weight and hemoglobin levels 4
Pregnancy: IV iron is appropriate during second and third trimesters when oral iron is insufficient 2
Chronic kidney disease and cancer patients: IV iron is preferred due to inflammation-mediated hepcidin upregulation that impairs oral iron absorption 1, 2
Practical Approach
Before Ordering IV Iron
Confirm you've attempted oral iron therapy (unless contraindicated) with ferrous sulfate 325 mg daily or every other day, ideally with vitamin C supplementation 1. A trial period of 3-6 months is often needed to assess oral iron efficacy 5
Choosing IV Iron Formulations
Prefer formulations requiring 1-2 infusions over those requiring multiple doses for patient convenience 1. Options include ferric carboxymaltose (up to 1,000 mg per dose) or iron dextran (total dose infusion) 1, 4
Safety Considerations
All IV iron formulations have similar safety profiles, with true anaphylaxis being very rare 1. Most reactions are complement activation-related pseudo-allergy (infusion reactions) rather than true allergic responses 1
Monitor serum phosphate levels in patients requiring repeat courses within 3 months or those at risk for hypophosphatemia 4, 6
Common Pitfalls to Avoid
- Don't delay IV iron in malabsorption states: Patients with celiac disease, post-bariatric surgery, or active IBD inflammation will not respond adequately to oral iron 1, 2
- Don't confuse infusion reactions with anaphylaxis: Treat complement activation reactions appropriately rather than discontinuing all IV iron 1
- Don't use IV iron during active infection: Iron supplementation may promote bacterial growth and inflammation 1
- Don't forget to investigate the underlying cause: Identify and treat sources of blood loss or malabsorption before or concurrent with iron replacement 1, 2