EmpeiriaIron saturation
Also known as
TSAT, transferrin saturation, iron saturation
derived index · no single molecular formula
What this substance is
Transferrin saturation (%) = serum iron / total iron-binding capacity x 100
Derived from iron_serum.
Each molecule is drawn from ChEBI's curated 2D drawing, accepted only after its InChIKey, formula and charge matched the ChEBI release. Atom diagrams are checked against the NIST Atomic Spectra Database.
3D model · iron(3+)
A schematic atom: a nucleus of 26 protons and 30 neutrons (the most common isotope, 56Fe), inside its electron shells, 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵. The configuration matches the NIST Atomic Spectra Database ground state of Fe IV (6S<5/2>). The cloud is drawn as nested spheres because that term is an S state: the electron density really is spherical. Not to scale: shells are spaced on a square-root scale so the inner ones stay visible, and the nucleus is magnified about ten-thousand-fold.
Reference ranges
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This open edition shows a range only where a public-domain or openly licensed source states one, and none does for this marker yet. Compare your result with the range printed on your own lab report.
How it is measured
In practice
Transferrin saturation is worked out from other iron results on the same blood sample, so it is not a separate test. Blood is taken from a vein. You may be asked not to eat or drink for 8 hours first. A morning sample is preferred because iron levels change during the day.
Calculated, not measured: from serum iron and UIBC on the same specimen, TIBC = Fe + UIBC and saturation = Fe/(Fe + UIBC) x 100. Specimen is serum (or lithium heparin plasma, about 6% lower) separated from the clot within one hour and free of hemolysis; EDTA, citrate and oxalate are unacceptable. A fasting morning specimen is preferred because of diurnal variation; MedlinePlus advises 8 hours without food or drink.
Before the test
- Do not eat or drink for 8 hours before the test.
- Have the blood drawn in the morning if possible.
Where: laboratory
Sources: Laboratory Procedure Manual, Unsaturated Iron-Binding Capacity (UIBC) (NHANES 2017-March 2020), CDC National Center for Health Statistics; Total iron binding capacity, MedlinePlus Medical Encyclopedia cited · not yet checked by a person
In the lab
Serum iron divided by TIBC
Iron travels in the blood on a carrier protein. This test shows what percent of the carrier's seats are filled with iron.
Transferrin saturation (%) = serum iron / TIBC × 100, where TIBC is commonly calculated as serum iron + unsaturated iron-binding capacity (UIBC); iron and UIBC are each measured colorimetrically with FerroZine.
- Read by: None directly; derived from measured serum iron and UIBC (FerroZine colour, 546 nm)
Sources: CDC NHANES 2017-2018 Data Documentation: Iron Status - Serum (FETIB_J); CDC NHANES 2017-2018 Laboratory Procedure Manual: Unsaturated Iron-Binding Capacity (UIBC) cited · not yet checked by a person
What it reports on
-
liver
regulated by
The liver makes most transferrin and the hormone hepcidin, which controls how much iron enters the blood.
Associated symptoms
Conditions this marker features in
-
high
Iron overload
· supportive
A raised transferrin saturation (over 45%), with a raised ferritin, is what prompts gene testing. The gene test, not the saturation, confirms the diagnosis.
- low Low iron causing anaemia · supportive