Transferrin Saturation (TSAT) Calculator
Enter serum iron plus whichever second value your panel reports. Labs differ: some print TIBC, some UIBC, some transferrin. Switch the toggle to match your report rather than converting by hand.
Educational tool, not a diagnosis. TSAT is interpreted alongside ferritin, not instead of it — ferritin rises with inflammation and can look normal while iron stores are genuinely low, which is exactly when TSAT is most useful. A persistently high TSAT, particularly above 45%, is the standard trigger for investigating hemochromatosis. Reference intervals vary between laboratories; compare against the range printed on your report.
Why TSAT catches what ferritin misses
Ferritin is the marker most people know, and it is a good one — but it has a well-documented blind spot. Ferritin is an acute-phase reactant, meaning it rises with inflammation, infection, obesity and liver disease regardless of how much iron you actually have. That is how someone can be told their ferritin is normal while being genuinely iron deficient.
Transferrin saturation is not distorted the same way. It measures how much of your iron-carrying capacity is actually in use, so a low TSAT alongside a normal-looking ferritin is one of the most informative patterns on a panel — and it is exactly the case covered in ferritin versus iron saturation.
Reading it alongside the rest of your panel
TSAT is rarely interpreted alone. Low TSAT with normal hemoglobin suggests depletion that has not yet become anemia. Low TSAT with a low MCV and MCH points toward established iron-deficiency anemia. If you have been supplementing without improvement, the reasons are covered in why iron supplements stop working.