Ferritin and TSAT Cutoffs to Stop Oral Iron Supplementation
Stop oral iron supplementation when ferritin reaches ≥800 ng/mL AND TSAT ≥20%, or when TSAT reaches ≥40% regardless of ferritin level. 1
Evidence-Based Stopping Criteria
The most rigorous stopping criteria come from the 2023 KDIGO Controversies Conference, which analyzed phase 3 clinical trials in CKD patients. The iron stopping protocol used in the ASCEND-ND trial specified discontinuation when ferritin ≥800 ng/mL AND TSAT ≥20%, OR when TSAT ≥40% alone. 1 This dual-threshold approach prevents iron overload while ensuring adequate iron stores.
Primary Stopping Thresholds
- Ferritin ≥800 ng/mL with TSAT ≥20%: This combination indicates iron repletion with adequate mobilization capacity 1
- TSAT ≥40% alone: This threshold signals sufficient circulating iron regardless of ferritin, as TSAT >40% indicates iron sufficiency and potential for toxicity 1
Context-Specific Considerations
For cancer-related anemia, the 2014 American Journal of Hematology guidelines suggest stopping iron when ferritin >800 ng/mL or TSAT >50%, defining this range as "iron replete" status. 1 This slightly higher TSAT threshold reflects the functional iron deficiency common in malignancy.
For general iron deficiency anemia without inflammation, recent 2025 evidence suggests that ferritin levels of 30-45 ng/mL may be adequate for symptom resolution in non-inflammatory states. 2, 3 However, these represent starting thresholds for diagnosis, not stopping criteria for supplementation.
Clinical Algorithm for Discontinuation
Step 1: Measure Both Parameters
- Check ferritin AND TSAT simultaneously—never rely on ferritin alone 4
- TSAT is the more reliable functional indicator of iron status 4
Step 2: Apply Stopping Criteria
- Stop immediately if TSAT ≥40% (regardless of ferritin) 1
- Stop if ferritin ≥800 ng/mL AND TSAT ≥20% 1
- Continue if ferritin <800 ng/mL and TSAT <40% 1
Step 3: Safety Ceiling
- Never exceed ferritin >800 ng/mL in routine practice, as this approaches iron overload territory 1
- The upper safety limit for ferritin in cancer patients is 1200 ng/mL, but this should not be a target 1
Critical Pitfalls to Avoid
Do not use ferritin <100 ng/mL alone as a continuation criterion. While this threshold is used to start iron therapy, it does not inform when to stop. 5, 2 Ferritin can remain low in inflammatory states despite adequate iron stores.
Do not ignore TSAT when making stopping decisions. A 2024 heart failure analysis demonstrated that TSAT <20% is the most reliable indicator of true iron deficiency, while ferritin alone (especially <100 ng/mL) lacks pathophysiological validity for treatment decisions. 4 This principle applies to stopping criteria as well—TSAT ≥40% signals adequate iron regardless of ferritin.
Avoid continuing oral iron in patients with persistent low TSAT despite rising ferritin. This pattern (ferritin >100 ng/mL with TSAT <20%) suggests functional iron deficiency where oral iron is ineffective. 1, 5 These patients require IV iron, not continued oral supplementation.