Should we administer IV (Intravenous) iron to a patient with symptomatic anemia, impaired renal function, elevated ferritin, and low serum iron, who previously was not considered for IV iron therapy?

Yes, Administer IV Iron in This Clinical Scenario

In a patient with symptomatic anemia, impaired renal function, elevated ferritin, and low serum iron (low TSAT), you should administer IV iron because this represents functional iron deficiency—a state where iron is sequestered and unavailable for erythropoiesis despite seemingly adequate stores. 1

Understanding Functional Iron Deficiency

The key diagnostic feature here is the discordance between elevated ferritin and low serum iron/TSAT:

• Ferritin is an acute-phase reactant that rises independently during inflammation, chronic kidney disease, or tissue damage, masking the true iron availability for red blood cell production 1
• Inflammation-driven hepcidin elevation blocks intestinal iron absorption and traps iron in macrophages, creating functional iron deficiency despite apparent adequate ferritin stores 1
• TSAT <20% indicates iron-restricted erythropoiesis regardless of ferritin level and is the critical parameter for treatment decisions 1, 2

Treatment Threshold in Chronic Kidney Disease

The National Kidney Foundation KDOQI guidelines establish clear treatment criteria:

• Administer IV iron when TSAT is <20% even with ferritin levels up to 500-800 ng/mL in CKD patients 2, 1
• Additional iron should be given to patients with TSAT ≤20% and/or ferritin ≤100 ng/mL whenever anemia is present (Hct <33%), so long as administration does not chronically maintain TSAT >50% or ferritin >800 ng/mL 2
• The goal of iron therapy is to improve erythropoiesis, not to attain specific ferritin levels—functional iron deficiency can exist despite ferritin >100 ng/mL 2

Dosing and Administration

For patients with chronic kidney disease:

• Ferric carboxymaltose can be administered as 750 mg IV in two doses separated by at least 7 days (total 1,500 mg per course) for patients ≥50 kg 3
• Alternative: 15 mg/kg body weight up to maximum 1,000 mg as a single dose 3
• For hemodialysis patients: 1,000 mg IV iron over 8-10 weeks (typically 100-125 mg weekly) is standard 2
• Iron sucrose or ferric gluconate may be used in multiple smaller doses of 125 mg per session 1

Safety Considerations

Upper safety thresholds to avoid iron overload:

• Temporarily withhold IV iron if TSAT exceeds 50% or ferritin exceeds 800 ng/mL 2
• Monitor serum ferritin and TSAT at least every 3 months during maintenance therapy 2
• In hemodialysis patients, ferritin levels will decline naturally with repetitive dialyzer blood losses when IV iron is withheld, preventing sustained overload 2
• Clinical judgment is required when ferritin >800 ng/mL—balance the probability of hemoglobin improvement against infection/cardiovascular risks 1

Common Pitfall to Avoid

The critical error is withholding IV iron based solely on elevated ferritin without considering TSAT. This misses functional iron deficiency and perpetuates symptomatic anemia with its associated morbidity and mortality 2, 1. In CKD patients with inflammation, ferritin can be elevated (200-800 ng/mL) while TSAT remains low, indicating that iron is sequestered and unavailable—this scenario absolutely requires IV iron supplementation 1, 2.

Monitoring After Treatment

• Assess hemoglobin response after 1-2 months of IV iron therapy 2
• If no increase in hemoglobin but TSAT or ferritin increases, reduce weekly IV iron dose to the lowest amount required to maintain TSAT ≥20% and ferritin ≥100 ng/mL 2
• If hemoglobin increases at constant erythropoietin dose (if applicable), continue IV iron to achieve target hemoglobin 11-12 g/dL 2
• Check serum phosphate levels in patients requiring repeat courses within 3 months, as hypophosphatemia can occur 3