This transferrin saturation calculator computes TSAT — the percentage of iron-binding sites on transferrin that are actually occupied — from serum iron and TIBC, the iron-study ratio that separates deficiency from overload.

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TSAT = Serum Iron ÷ TIBC × 100 — Occupancy of the Iron Shuttle

Transferrin is the blood’s iron courier; saturation reports how full the courier fleet runs. It interprets alongside ferritin (storage) and the CBC — never as a solo diagnosis. Part of our Health Calculators collection.

Worked Example (Verified)

  • Iron 60 µg/dL, TIBC 300 µg/dL (defaults): 60/300 = 20.0% — the low edge of normal, classic early iron deficiency territory when ferritin agrees
  • Deficiency pattern: iron falls AND TIBC rises (the liver makes more empty couriers): 40/450 ≈ 8.9% — the ratio amplifies both signals
  • Overload pattern: iron high, TIBC normal-low: 180/280 ≈ 64% — the fasting TSAT that triggers HFE workup in screening guidelines
  • Anemia of inflammation: iron low, TIBC low-normal (couriers sequester iron deliberately): 35/220 ≈ 16% with high ferritin — TSAT plus ferritin untangles what neither does alone

Reading Iron Studies as a Panel

  • Ferritin = storage gauge (but also an acute-phase reactant).
  • Serum iron = cargo in transit at this hour (diurnal, meal-sensitive).
  • TIBC = fleet size (rises in deficiency and pregnancy, falls in inflammation and overload).
  • TSAT = occupancy rate — the ratio that normalizes cargo by fleet.

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Frequently Asked Questions

How do you calculate transferrin saturation?

TSAT (%) = serum iron ÷ TIBC × 100, both in µg/dL. Iron 60 with TIBC 300 gives 20%. If your lab reports UIBC instead, TIBC = serum iron + UIBC. Fasting morning values are the standard because serum iron varies through the day.

What is a normal transferrin saturation?

Reference ranges run roughly 16–50% (labs vary; some quote 20–50% for men, slightly lower for women). Below ~16–20% suggests iron supply is limiting red-cell production; persistently above ~45–50% fasting prompts iron-overload evaluation.

What does low TSAT mean?

Iron delivery is falling short of marrow demand — most often true iron deficiency (blood loss, low intake, malabsorption), though inflammation also lowers iron and TSAT while ferritin climbs. The panel pattern (ferritin, TIBC direction) discriminates the two.

What does high TSAT mean?

Iron supply is outrunning binding capacity — seen in hereditary hemochromatosis (often the earliest abnormal test), transfusional overload, liver disease, and after IV iron. A single high value is rechecked fasting before conclusions; persistent fasting elevation > 45% is the classic screening trigger.

TSAT vs ferritin — which matters more?

They answer different questions: ferritin gauges stored iron; TSAT gauges circulating delivery. Deficiency is most convincing when both point the same way (low ferritin + low TSAT); discordance (high ferritin, low TSAT) usually signals inflammation layered on the picture.

Is this transferrin saturation calculator free?

Yes — free, instant, no sign-up. An educational aid for understanding lab results, not a diagnosis.