Iron Supplementation Should Be Discontinued
With iron saturation levels consistently between 49-62% (well above the 20% minimum target and approaching the 50% upper safety threshold) and ferritin ≤52 ng/mL, you should discontinue oral iron supplementation to prevent iron overload while the ferritin remains low enough to avoid toxicity concerns.
Interpretation of Your Patient's Iron Parameters
Your patient presents an unusual pattern that requires careful analysis:
Iron saturation of 49-62% indicates adequate to excessive circulating iron availability for erythropoiesis, as this exceeds the 20% minimum target established by KDIGO and NKF-K/DOQI guidelines 1. Values approaching or exceeding 50% warrant withholding iron therapy 1.
Ferritin ≤52 ng/mL appears low but may not reflect true iron deficiency in this context. The discordance between high transferrin saturation and low ferritin is clinically significant. Recent evidence demonstrates that ferritin levels between 20-300 ng/mL lie entirely within normal ranges for healthy adults 2, and a ferritin >50 μg/L can still be consistent with adequate iron stores in many patients 3.
The 48-hour washout period before testing is appropriate and ensures these values reflect true iron status rather than acute supplementation effects 4.
Evidence-Based Stopping Criteria Met
Your patient meets clear criteria for iron discontinuation based on transferrin saturation alone:
Guidelines from NKF-K/DOQI explicitly recommend withholding IV iron when TSAT exceeds 50%, with monitoring for up to 3 months 1. Your patient's values of 49-62% are at or above this threshold.
KDIGO consensus data show that iron-stopping criteria include TSAT >40% in multiple clinical trial protocols 1. Your patient consistently exceeds this level.
Transferrin saturation is the more reliable indicator of iron deficiency and repletion status compared to ferritin, particularly in determining clinical benefit from iron therapy 2. A TSAT <20% identifies true iron deficiency, while your patient's TSAT of 49-62% indicates iron sufficiency.
Safety Concerns With Continued Therapy
Continuing iron supplementation poses specific risks:
Risk of progressive iron overload: Even low-dose continuous iron therapy (31.25 mg weekly) can lead to positive iron balance and ferritin values exceeding 500 ng/mL in 33% of patients within 12 months 5. Your patient's high TSAT suggests ongoing iron absorption despite supplementation being held.
Transferrin saturation chronically above 50% should be avoided per NKF-K/DOQI recommendations to prevent iron toxicity 1.
The low ferritin does not mandate continued therapy when TSAT is adequate. Ferritin can be falsely low or slow to rise even with adequate iron stores 3, 4, and the TSAT is the more mechanistically relevant parameter for assessing iron availability for erythropoiesis 2.
Common Pitfall to Avoid
Do not reflexively continue iron based solely on ferritin <100 ng/mL when TSAT is elevated. This represents outdated thinking from renal anemia protocols that has been challenged by recent evidence 2. The combination of high TSAT with low-normal ferritin suggests either:
- Adequate functional iron with low storage iron (supplementation not needed)
- Possible inflammation or other factors affecting ferritin measurement
- Individual variation in iron metabolism
Recommended Management Algorithm
Discontinue oral iron supplementation immediately given TSAT 49-62% 1, 6
Recheck iron studies (ferritin, TSAT, hemoglobin) in 3 months after discontinuation 1, 6
Resume iron only if BOTH conditions develop:
Monitor for symptoms of anemia during the observation period, though with TSAT >45%, this is unlikely 1
If ferritin rises while off supplementation, this confirms iron overload was developing and validates the decision to stop 5