What is a normal transferrin saturation?

Normal TSAT is 20–50%. TSAT 45% raises suspicion for iron overload (hereditary hemochromatosis screening threshold). TSAT < 20% with elevated ferritin suggests functional iron deficiency (common in chronic disease and CKD).

When should transferrin saturation be checked?

Check TSAT when evaluating anemia (especially microcytic), screening for hereditary hemochromatosis (TSAT > 45%), monitoring iron therapy in CKD (target TSAT 20–50%), and evaluating iron overload in transfusion-dependent patients. Morning fasting samples are preferred as serum iron has diurnal variation.

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Transferrin Saturation (TSAT) Calculator

Calculate TSAT% from serum iron and total iron-binding capacity (TIBC). Essential for evaluating iron deficiency anemia and hemochromatosis.

Inputs

Serum Iron (mcg/dL)

TIBC (mcg/dL)

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Enter serum iron and TIBC to calculate.

< 20%Iron deficiency (consider IV iron if CKD/CHF)

20–50%Normal range

> 45%Screen for hemochromatosis (check HFE gene)

> 50% (women) / > 60% (men)Suggestive of iron overload

Disclaimer: For educational purposes only. Not a substitute for clinical judgment.

When to use

TSAT is a key component of iron studies used to evaluate microcytic anemia, screen for hereditary hemochromatosis, and guide IV iron therapy in CKD and heart failure patients.

Clinical pearls

Formula: TSAT% = (Serum Iron ÷ TIBC) × 100
Fasting morning samples are most accurate — serum iron has significant diurnal variation.
TSAT < 20% with ferritin < 30 ng/mL = iron deficiency anemia.
In CKD patients on ESAs, target TSAT ≥ 20% and ferritin ≥ 100 ng/mL (or ≥ 200 for hemodialysis).
TSAT > 45% is the recommended threshold for hemochromatosis screening (AASLD guidelines).

References

Bacon BR, et al. Diagnosis and management of hemochromatosis: 2011 AASLD practice guideline. Hepatology. 2011;54(1):328-343.
KDIGO 2012 Clinical Practice Guideline for Anemia in CKD. Kidney Int Suppl. 2012;2(4):279-335.

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About This Tool

What Is Transferrin Saturation?

Transferrin saturation (TSAT) represents the percentage of transferrin binding sites occupied by iron. Transferrin is the primary iron transport protein in serum. TSAT is calculated as serum iron divided by total iron-binding capacity (TIBC), multiplied by 100. It reflects the availability of iron for erythropoiesis and is a more dynamic marker than ferritin, which is an acute phase reactant.

Iron Deficiency vs Iron Overload

In iron deficiency, TSAT is low (< 20%) because serum iron drops while TIBC increases (the body upregulates transferrin production to capture more iron). In iron overload (hemochromatosis), TSAT is elevated (> 45-60%) because iron saturates available binding sites. Importantly, TSAT should be interpreted alongside ferritin, as inflammation can confound iron studies.

🔑 Clinical Pearls

Iron deficiency anemia: ↓ TSAT, ↓ ferritin, ↑ TIBC. Anemia of chronic disease: ↓ TSAT, ↑ ferritin, ↓ TIBC.
Ferritin < 30 is diagnostic of iron deficiency. Ferritin 30-100 with TSAT < 20% is still likely iron deficient.
TSAT > 45% on fasting morning sample × 2 occasions → check HFE gene testing for hereditary hemochromatosis.
In CKD patients on dialysis, KDIGO recommends maintaining TSAT 20-30% and ferritin 200-500 for ESA-treated patients.

Key References

Camaschella C. Iron-deficiency anemia. NEJM. 2015;372(19):1832-1843.
Bacon BR, et al. Diagnosis and management of hemochromatosis: 2011 AASLD practice guideline. Hepatology. 2011;54(1):328-343.

Formula last verified: February 2026