Transferrin Saturation Calculator
Calculate transferrin saturation (TSAT) from an iron panel. Enter serum iron and total iron-binding capacity (TIBC) in the same units (µg/dL by default) to get TSAT as a percentage, its band, and the UIBC.
Example: with Serum iron (µg/dL) 100 · TIBC (µg/dL) 350 → Transferrin saturation (TSAT): 28.6%.
- Interpretation20% to 45% — within the usual reference range
- UIBC (unsaturated binding capacity)250 µg/dL (TIBC − iron)
Computed by the calculator below using its default values. Change any input to see your own numbers.
TSAT = serum iron ÷ TIBC × 100. Because it is a ratio, iron and TIBC just have to be in the same units — the percentage comes out the same in µg/dL or µmol/L.
What transferrin saturation shows
Transferrin is the protein that ferries iron through the blood. TIBC (total iron-binding capacity) reflects how many transferrin seats are available; serum iron is how many are filled. TSAT is simply the percentage of those seats occupied — iron divided by TIBC, times 100. A saturation near 25 to 35 percent is typical when iron balance is healthy.
Low TSAT means transferrin is going hungry: the classic pattern of iron deficiency, where iron falls and TIBC rises, driving the percentage down. High TSAT means the seats are overfilled, which raises the question of iron overload or hereditary hemochromatosis. Because TSAT reflects transport rather than stores, it is read alongside ferritin, which reflects the reserve.
How it’s calculated
TSAT (%) = serum iron ÷ TIBC × 100. UIBC (unsaturated iron-binding capacity) = TIBC − serum iron. Iron and TIBC must be in the same units; the ratio is unit-independent (µg/dL ÷ µg/dL or µmol/L ÷ µmol/L). Reference band roughly 20–45%, with iron deficiency below and overload above.
Cutoffs vary by lab and sex (some cite up to 50% as normal). Fasting, recent iron intake, inflammation, and time of day all shift iron. This is educational — interpret with ferritin and a clinician, not alone.
Transferrin saturation bands
| TSAT | Interpretation |
|---|---|
| Under 20% | Low — suggests iron deficiency |
| 20% – 45% | Typical reference range |
| Over 45% | Elevated — consider iron overload / hemochromatosis |
| Over 45% men, 50% women | Common screening thresholds for overload |
Source: commonly published transferrin saturation reference and hemochromatosis screening thresholds.
Common mistakes
- Entering iron and TIBC in different units; they must match for the ratio to be valid.
- Reading TSAT without ferritin — transport and storage tell different parts of the story.
- Ignoring inflammation, which lowers TIBC and can mask or mimic iron problems.
- Using a non-fasting sample after iron supplements, which transiently spikes serum iron.
Frequently asked questions
How do you calculate transferrin saturation?
Divide serum iron by TIBC and multiply by 100. For example, iron 100 µg/dL over a TIBC of 350 µg/dL gives 100 ÷ 350 × 100 = about 28.6 percent.
What is a normal TSAT?
Roughly 20 to 45 percent, though labs vary. Below about 20 percent suggests iron deficiency, and above 45 to 50 percent raises the possibility of iron overload or hemochromatosis.
Do the units of iron and TIBC matter?
They must match, but the ratio itself is unit-independent. Iron and TIBC both in µg/dL, or both in µmol/L, give the same percentage.
What is UIBC?
Unsaturated iron-binding capacity is TIBC minus serum iron — the transferrin seats still empty. Some labs measure UIBC and iron directly and derive TIBC as their sum.
Should a high or low TSAT worry me?
It is a flag, not a diagnosis. Bring an abnormal result to your doctor, who will check ferritin and other tests before deciding what, if anything, it means for you.