Does This Patient Have Functional Iron Deficiency Requiring IV Iron?
No, this patient does not meet criteria for functional iron deficiency and should not receive intravenous iron. Her ferritin of 313 ng/mL with a transferrin saturation of 15% and hemoglobin of 13.1 g/dL does not indicate iron deficiency requiring IV iron therapy, and her hemoglobin is above the threshold where treatment would provide meaningful benefit.
Diagnostic Assessment
Iron Status Interpretation
This patient's iron parameters do not indicate functional iron deficiency:
Ferritin 313 ng/mL is well above deficiency thresholds. Functional iron deficiency is defined as ferritin 100-300 ng/mL with transferrin saturation <20% in heart failure patients 1, or ferritin 30-800 ng/mL with TSAT 20-50% in cancer patients 1. Her ferritin of 313 ng/mL exceeds the upper limit for functional iron deficiency in most guideline definitions 1.
The low transferrin saturation (15%) with elevated ferritin suggests inflammation, not iron deficiency. In chronic kidney disease, absolute iron deficiency is defined as ferritin <100 ng/mL AND TSAT <20% 1. When ferritin is elevated (>100 ng/mL) but TSAT is low, this pattern typically indicates an inflammatory iron block rather than true iron deficiency 1.
Her hemoglobin of 13.1 g/dL is above anemia thresholds. The WHO defines anemia as hemoglobin <12 g/dL in women 1. This patient is not anemic and therefore would not benefit from iron therapy aimed at correcting anemia.
Clinical Context Matters
The indication for IV iron depends heavily on the underlying condition:
Heart failure patients: IV iron is reasonable (Class IIb) when ferritin <100 ng/mL OR ferritin 100-300 ng/mL with TSAT <20%, but only in NYHA class II-III patients to improve functional status and quality of life 1. This patient's ferritin of 313 ng/mL exceeds these criteria.
Cancer patients on chemotherapy: Functional iron deficiency is defined as TSAT 20-50% with ferritin 30-800 ng/mL 1. This patient's TSAT of 15% is below this range, and there is no mention of active malignancy or chemotherapy.
Chronic kidney disease patients: Target iron levels require TSAT ≥20% and ferritin ≥100 ng/mL 1. This patient meets the ferritin target but not the TSAT target, suggesting possible inflammation rather than deficiency.
Treatment Recommendation
Why IV Iron Is Not Indicated
Multiple factors argue against IV iron therapy in this patient:
No evidence of true iron deficiency. Her elevated ferritin indicates adequate iron stores 1, 2. The low TSAT with high ferritin pattern suggests inflammatory iron sequestration, where iron is present but not mobilized 1.
Hemoglobin is normal. At 13.1 g/dL, she has no anemia requiring correction 1, 2. IV iron studies have focused on patients with hemoglobin <11-12 g/dL 1.
Risk without clear benefit. IV iron carries risks including infusion reactions (<1% moderate-severe), hypophosphatemia (50-74% with ferric carboxymaltose causing the "6H syndrome" with potential bone complications), and interference with MRI interpretation for up to 6 months with ferrumoxytol 2, 3, 4.
Appropriate Next Steps
Instead of IV iron, the following approach is warranted:
Evaluate for inflammation or chronic disease. The elevated ferritin with low TSAT suggests an acute phase reaction 1. Check inflammatory markers (CRP, ESR) and evaluate for underlying inflammatory conditions 1.
Assess for causes of low TSAT beyond iron deficiency. In the setting of normal hemoglobin and elevated ferritin, low TSAT may reflect inflammatory iron sequestration rather than deficiency 1. If inflammation is present, treating the underlying condition is more appropriate than iron supplementation.
Consider oral iron only if true deficiency is confirmed. If after evaluation for inflammation, iron deficiency is still suspected, oral iron is first-line therapy 2. The American Gastroenterological Association recommends oral iron as first-line treatment for mild iron deficiency anemia 2.
Monitor iron parameters. Recheck ferritin, TSAT, and hemoglobin in 4-8 weeks 2. If ferritin continues to rise or remains elevated with persistent low TSAT, this confirms inflammatory iron block rather than deficiency 1.
Common Pitfalls to Avoid
Do not reflexively treat low TSAT with IV iron when ferritin is elevated:
Low TSAT with high ferritin indicates inflammation, not iron deficiency. This pattern is seen with inflammatory iron block where hepcidin prevents iron mobilization from stores 1. Giving IV iron in this setting adds to already adequate stores without improving iron availability.
Surgical menopause alone does not justify IV iron. While menstruating women have higher iron requirements, post-menopausal women (including surgical menopause) have lower iron needs and are at lower risk for iron deficiency 1.
IV iron is not benign. Recent evidence highlights significant complications, particularly hypophosphatemia with ferric carboxymaltose affecting 50-74% of patients, potentially causing osteomalacia and fractures 3. These risks must be weighed against potential benefits.