Indications for Intravenous Iron Therapy
Intravenous iron should be used when patients cannot tolerate oral iron, fail to respond to oral iron therapy, or have conditions where oral iron absorption is compromised. 1
Primary Indications for IV Iron
General Indications (All Patients with Iron Deficiency Anemia)
Use IV iron as first-line therapy in the following situations: 1
- Oral iron intolerance – patients experiencing gastrointestinal side effects that prevent continuation 1
- Failure to improve ferritin levels after an adequate trial of oral iron 1
- Conditions with impaired iron absorption where oral iron is unlikely to be effective 1
- Hemoglobin below 10 g/dL – severe anemia requiring rapid iron repletion 1
Disease-Specific Indications
Inflammatory Bowel Disease (IBD)
IV iron is the preferred first-line treatment in IBD patients with: 1
- Active inflammation with compromised absorption – inflammation impairs iron absorption and oral iron may exacerbate disease activity 1
- Hemoglobin below 10 g/dL (100 g/L) regardless of disease activity 1
- Previous intolerance to oral iron 1
- Need for erythropoiesis-stimulating agents (ESAs) 1
The European Crohn's and Colitis Organization emphasizes that IV iron is more effective, shows faster response, and is better tolerated than oral iron in IBD patients 1. Oral iron may be reserved for patients with mild anemia (Hb 11.0-11.9 g/dL in women, 11.0-12.9 g/dL in men), clinically inactive disease, and no prior oral iron intolerance 1.
Chronic Kidney Disease (CKD)
IV iron is indicated for CKD patients when: 1, 2
- Oral iron fails to meet iron status targets despite maximally tolerated doses 1
- Patients are on hemodialysis with ongoing iron losses 1
- Oral iron is not tolerated 1
Iron sucrose is FDA-approved specifically for treatment of iron deficiency anemia in patients with chronic kidney disease 2.
Heart Failure with Iron Deficiency
IV iron is indicated for patients with heart failure (NYHA class II/III) and iron deficiency to improve exercise capacity, even in the absence of anemia 3. The American Gastroenterological Association notes beneficial effects on functional capacity and quality of life 1.
Dosing is based on body weight and hemoglobin levels, with maintenance doses administered if serum ferritin remains <100 ng/mL or ferritin 100-300 ng/mL with transferrin saturation <20% 3.
Post-Bariatric Surgery
IV iron should be used in patients who have undergone bariatric procedures that disrupt normal duodenal iron absorption, particularly when they have iron deficiency anemia without identifiable chronic gastrointestinal blood loss 1.
Celiac Disease
Consider IV iron when patients with celiac disease and iron deficiency anemia fail to improve iron stores despite adherence to a gluten-free diet and oral iron supplementation 1.
Portal Hypertensive Gastropathy
Use IV iron in patients with ongoing bleeding who do not respond to oral iron therapy, though oral iron should be attempted initially 1.
Pregnancy and Heavy Menstrual Bleeding
IV iron is indicated during the second and third trimesters of pregnancy when oral iron is ineffective or not tolerated 4, 5. It is also appropriate for heavy menstrual bleeding when rapid iron repletion is needed 6, 4.
Practical Considerations
Formulation Selection
Prefer IV iron formulations that can replace iron deficits with 1 or 2 infusions over those requiring more than 2 infusions 1. Ferric carboxymaltose allows single doses up to 1,000 mg and can be administered over 15 minutes 1, 3, while iron sucrose is limited to 200 mg per dose 1.
Safety Profile
All IV iron formulations have similar risks; true anaphylaxis is very rare 1. The vast majority of reactions are complement activation-related pseudo-allergy (infusion reactions) rather than true allergic reactions and should be treated accordingly 1. Modern IV iron preparations have an excellent overall safety profile 7.
Monitoring for Repeat Treatment
Check serum phosphate levels in patients requiring repeat courses of treatment, especially if administered within three months, as hypophosphatemia is a recognized adverse effect 3, 7.