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Transferrin Saturation (TSAT)

Transferrin saturation = serum iron ÷ TIBC × 100. Normal is roughly 20–45%; <20% supports iron deficiency (absolute or functional), and a fasting value ≥45% warrants evaluation for iron overload (HFE haemochromatosis).

Serum iron (µg/dL or µmol/L)
Total iron-binding capacity (TIBC) (µg/dL or µmol/L)

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Interpretation

Result	Meaning
< 20%	Iron deficiency (with ferritin) or functional deficiency
20–45%	Normal
≥ 45%	Possible iron overload

Formula

TSAT (%) = serum iron ÷ TIBC × 100 (same units). If only transferrin (mg/dL) is available: TIBC (µg/dL) ≈ transferrin × 1.25.

Clinical pearls

Serum iron has diurnal variation and rises after meals: use a fasting morning sample for overload screening.
In CKD and heart failure, TSAT <20% with ferritin <300–500 ng/mL defines iron deficiency suitable for IV iron.

Examples

transferrin saturation iron 50 tibc 400 tsat serum iron 32 umol/L TIBC 54 umol/L iron 180 tibc 300 iron overload?

FAQ

What is a normal transferrin saturation?

About 20–45% in adults; reference ranges vary slightly by lab and sex.

What TSAT suggests haemochromatosis?

A fasting transferrin saturation of 45% or higher, especially with raised ferritin, should prompt HFE testing.

Evidence

Bacon BR et al. Diagnosis and management of hemochromatosis: 2011 practice guideline by the AASLD. Hepatology 2011;54:328–43.

Hematology & Oncology · Reviewed 2026-10-14 · Methodology