Lab Reference Library / Transferrin Saturation
Nutritional & Micronutrient
Transferrin Saturation
TSAT · Iron Saturation · Transferrin Saturation %Reference range, optimal functional medicine levels, and why transferrin saturation is the most sensitive measure of current iron delivery to tissues, why it detects both iron deficiency and iron overload more reliably than serum iron alone, and how to interpret it in the complete iron panel.
Most SearchedIron Status
Standard Range20 to 50%
FM Optimal25 to 40%
Iron DeficiencyBelow 16%
Units%
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Category: Nutritional & Micronutrient | Also known as: TSAT, Iron Saturation %, Iron Saturation
1. What This Test Measures
Transferrin saturation (TSAT) is calculated by dividing serum iron by TIBC multiplied by 100, expressing the percentage of transferrin currently bound to iron. It is the most direct measure of iron delivery to erythropoietic and other tissues at the moment of testing. TSAT falls in iron deficiency and rises in iron overload.
2. Optimal Range and Thresholds
| TSAT Level | Interpretation |
|---|---|
| Below 16% | Iron-restricted erythropoiesis: anemia developing |
| 16 to 25% | Low-normal: suboptimal; evaluate ferritin and clinical context |
| 25 to 40% | Optimal: adequate iron transport without excess |
| 40 to 50% | High-normal: borderline; evaluate ferritin for iron overload |
| Above 45 to 50% | Elevated: iron overload likely; screen for hemochromatosis |
3. TSAT in Iron Panel Pattern Interpretation
TSAT above 45% with elevated ferritin is the primary hemochromatosis screening signal. Hereditary hemochromatosis from HFE gene mutations (C282Y, H63D) affects approximately 1 in 250 people of Northern European ancestry. HFE gene testing should follow elevated TSAT and ferritin. Untreated hemochromatosis causes liver cirrhosis, diabetes, cardiomyopathy, and arthropathy over decades.
4. Pattern Interpretation
- Low TSAT + low ferritin + high TIBC: iron deficiency anemia; iron supplementation indicated
- Low TSAT + normal or high ferritin + normal or low TIBC: anemia of chronic disease; treat underlying inflammation
- High TSAT (above 45%) + high ferritin: hemochromatosis or iron overload; HFE gene testing; therapeutic phlebotomy
- High TSAT from recent supplement: always draw fasting without same-day iron
5. Related Lab Tests
FerritinIron Storage Companion Marker
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Serum IronNumerator in TSAT Calculation
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TIBCDenominator in TSAT Calculation
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ALTLiver Damage from Iron Overload
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HbA1cDiabetes from Hemochromatosis
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hs-CRPInflammation Suppresses TSAT via Hepcidin
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6. Clinical Perspective
Clinical Perspective
A TSAT of 52% with a ferritin of 380 in a 45-year-old man of Irish descent is not an incidental finding. That is hereditary hemochromatosis until proven otherwise, and the stakes of missing it are liver disease, diabetes, and cardiomyopathy over the next two decades. HFE gene testing and therapeutic phlebotomy initiated now can prevent all of that. Hemochromatosis is one of the most treatable genetic conditions in medicine, and the only reason it progresses to organ damage is that it was not caught early enough.
Brian Lamkin, DO | Founder, The Lamkin Clinic | Edmond, Oklahoma
7. Frequently Asked Questions
What is the optimal transferrin saturation?
Optimal TSAT is 25 to 40%. Below 16% indicates iron-restricted erythropoiesis. Above 45% with elevated ferritin warrants evaluation for hereditary hemochromatosis and HFE gene testing.
What does high transferrin saturation mean?
TSAT above 45% suggests iron excess with near-fully saturated transferrin. Combined with elevated ferritin, it is the primary signal for hereditary hemochromatosis. HFE gene testing and liver assessment should follow.
How is transferrin saturation calculated?
TSAT equals serum iron divided by TIBC multiplied by 100, expressed as a percentage. Draw fasting in the morning without same-day iron supplementation for most accurate results.
Content authored and clinically reviewed by Brian Lamkin, DO, founder of The Lamkin Clinic in Edmond, Oklahoma. Brian Lamkin, DO has 25+ years of experience in functional and regenerative medicine. This page reflects current functional medicine practice standards and is updated as new clinical evidence becomes available.
A TSAT above 45% with elevated ferritin is not a routine finding. It requires hemochromatosis evaluation.
The complete iron panel provides context that no single marker can. Schedule a consultation for a comprehensive iron status and metabolic assessment.
Schedule a ConsultationMedical Disclaimer: This content is provided for educational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Lab interpretation should always be performed in clinical context by a qualified healthcare provider. Reference ranges and optimal targets may vary based on individual patient history, clinical presentation, and laboratory methodology. Schedule a consultation to discuss your specific results with Dr. Lamkin.