Indications for Intravenous Iron Therapy
Intravenous iron is indicated for patients with documented iron deficiency anemia when oral iron is unsatisfactory, impossible, or contraindicated, and for specific clinical situations requiring rapid iron repletion. 1
Primary Indications
Absolute Indications for IV Iron
Oral iron intolerance or failure: Patients who cannot tolerate oral iron due to gastrointestinal side effects (nausea, constipation, gastric irritation) or who show inadequate response after appropriate trial 2, 1, 3
Malabsorption conditions: Patients with impaired iron absorption including:
Chronic kidney disease (CKD): All hemodialysis patients receiving erythropoiesis-stimulating agents (ESAs) due to high blood losses and functional iron deficiency 5
Ongoing significant blood loss: Patients with heavy uterine bleeding, hereditary hemorrhagic telangiectasia, or other sources of continuous blood loss 4, 3
Strong Indications for IV Iron
Severe anemia: Hemoglobin <10 g/dL (100 g/L), where rapid correction is needed 5
Pregnancy: Second and third trimesters when oral iron is insufficient 3
Chronic inflammatory conditions with functional iron deficiency:
Pronounced disease activity in IBD patients 5
ESA therapy: Patients receiving erythropoiesis-stimulating agents who require optimal iron availability to prevent functional iron deficiency 5
Clinical Scenarios and Laboratory Thresholds
For Hemodialysis Patients
Maintenance therapy: Regular small doses (25-100 mg weekly) to prevent iron deficiency and maintain transferrin saturation ≥20% and ferritin ≥100 ng/mL 5
Repletion therapy: When transferrin saturation <20% or ferritin <100 ng/mL despite oral iron 5
Functional iron deficiency: Even when ferritin is 100-500 ng/mL but hemoglobin remains <11 g/dL or high ESA doses are required 5
For Non-Dialysis CKD and Peritoneal Dialysis Patients
Inadequate response to oral iron: Transferrin saturation remains <20% or ferritin <100 ng/mL after appropriate oral iron trial 5, 2
ESA hyporesponsiveness: Requiring high ESA doses to maintain target hemoglobin 5
For IBD Patients
Mild anemia with active disease: Even with hemoglobin >10 g/dL if disease is active, as oral iron may exacerbate inflammation 5
Moderate to severe anemia: Hemoglobin <10 g/dL regardless of disease activity 5
Failure of oral iron: No improvement in iron parameters within 2 weeks of oral therapy 5
Special Considerations
When IV Iron Should Be Tried Before ESAs
CKD patients: KDIGO 2012 guidelines advocate a trial of IV iron prior to initiating ESA therapy 5
Hemodialysis patients: IV iron can reduce or eliminate ESA requirements, providing 20-30% cost savings 5
Acute Situations Requiring IV Iron
Hemodynamic instability from acute anemia 5
Severe anemia-related fatigue requiring rapid correction 5
Failure of other treatments in critical situations 5
Common Pitfalls to Avoid
Don't rely solely on ferritin in inflammatory states: Ferritin can be spuriously normal due to inflammation; use transferrin saturation <20% as the diagnostic criterion 6, 3
Don't delay IV iron in hemodialysis patients: Most will require IV iron to maintain adequate stores due to ongoing blood losses; oral iron is usually insufficient 5
Don't use oral iron in active IBD: Unabsorbed oral iron generates reactive oxygen species that may exacerbate disease activity 5
Monitor for hypophosphatemia: Particularly with ferric carboxymaltose, which causes hyperphosphaturic hypophosphatemia in 50-74% of patients, potentially leading to osteomalacia and fractures 6
Contraindications to Consider
While IV iron is generally safe with serious adverse events occurring in <1% of patients 6, avoid in patients with: