When to stop Zincofer (iron supplement) based on serum iron or ferritin levels?

When to Stop Zincofer (Iron Supplementation)

Stop Zincofer when serum ferritin reaches ≥800 ng/mL and/or transferrin saturation (TSAT) reaches ≥50%, as continuing iron beyond these thresholds provides no additional erythropoietic benefit and risks iron overload. 1

Clinical Context and Stopping Criteria

The decision to discontinue iron supplementation depends critically on your patient population and clinical indication:

For Chronic Kidney Disease Patients (Most Relevant Context)

Upper Safety Thresholds - Temporarily Withhold Iron When:

• Serum ferritin ≥800 ng/mL 1
• TSAT ≥50% 1
• Either threshold alone warrants stopping, even if the other parameter remains lower 1

Key Principle: The goal of iron therapy is to improve erythropoiesis, not to achieve specific ferritin or TSAT levels. 1 Patients are unlikely to respond with further increases in hemoglobin/hematocrit or reductions in erythropoietin requirements once ferritin reaches 800 ng/mL or TSAT reaches 50%. 1

Monitoring Strategy:

• Check TSAT and ferritin at least every 3 months during maintenance therapy 1
• Iron overload can be avoided by temporarily withholding IV iron when these levels become too high, given the repetitive blood losses in hemodialysis patients 1

For Non-CKD Populations (General Iron Deficiency)

Stop When Iron Stores Are Replete:

• Target ferritin: 50-100 ng/mL for maintenance 1
• Continue monitoring ferritin every 3-6 months after stopping 1
• Reinitiate iron only if ferritin drops below 50 ng/mL or clinical iron deficiency recurs 1

Important Caveats and Pitfalls

Ferritin as an Acute Phase Reactant:

• Ferritin levels can be falsely elevated during inflammation, infection, or malignancy 1
• In these situations, ferritin may not accurately reflect true iron stores 2
• Consider using TSAT as a complementary measure, as it is less affected by inflammation 1

Significant Measurement Variability:

• Ferritin assays can vary by up to 150 ng/mL between different laboratory methods 3
• Intraindividual variability ranges from 2-62% over short periods in stable patients 3
• Never base treatment decisions on a single ferritin value - trend multiple measurements over time 3

Context-Specific Considerations:

• In CKD patients on erythropoiesis-stimulating agents (ESAs), functional iron deficiency can exist even with ferritin ≥100 ng/mL and TSAT ≥20% 1
• Ferritin levels between 300-800 ng/mL have been common in dialysis patients without evidence of adverse iron-mediated effects 1
• There is no known risk associated with TSAT ≤50%, but no physiologic rationale for maintaining TSAT >50% 1

Algorithmic Approach to Stopping Zincofer

1. Identify patient population: CKD/dialysis vs. general iron deficiency
2. For CKD patients: Stop when ferritin ≥800 ng/mL OR TSAT ≥50% 1
3. For non-CKD patients: Stop when ferritin reaches 50-100 ng/mL 1
4. Verify with repeat testing in 2-4 weeks to confirm sustained elevation 3
5. Monitor hemoglobin - if anemia persists despite adequate iron stores, investigate other causes 1
6. Resume iron only if: ferritin drops below target thresholds or functional iron deficiency develops (low TSAT with adequate ferritin in CKD patients) 1