Transferrin saturation
Also called: TSAT, Iron saturation
The percentage of your iron-carrying protein (transferrin) that is actually loaded with iron. It is one of the iron studies and gives a clearer read on iron status than iron alone: a low saturation points to iron deficiency, while a high saturation flags iron overload, as in haemochromatosis.
Published: Updated:
Check your result
Calculated in your browser - the number is not sent anywhere.
Have the whole report? Upload it - we'll explain every value on it
What does Transferrin saturation measure?
Transferrin saturation is a calculated part of the iron studies. Iron travels in the blood attached to a carrier protein called transferrin, and the saturation is simply what percentage of the available transferrin binding sites are actually occupied by iron — the blood iron level divided by the total iron-binding capacity, expressed as a percentage. It is more informative than the iron level alone, because the iron level fluctuates through the day and with meals, whereas the saturation puts it in the context of how much carrier is available. A low transferrin saturation is a hallmark of iron deficiency: there is little iron relative to plenty of empty carrier, so the percentage falls. A high transferrin saturation points the other way, toward iron overload — most importantly hereditary haemochromatosis, an inherited condition where the body absorbs too much iron, but also iron overload from repeated transfusions or from taking too much iron. It is read together with ferritin (the body's iron store), the iron level and the total iron-binding capacity; the combination distinguishes iron deficiency, iron overload and the pattern seen in chronic inflammation, where iron is present but locked away.
What does a high Transferrin saturation level mean?
- Hereditary haemochromatosis — the classic cause; the body absorbs and stores too much iron.
- Iron overload from transfusions — in people who have had many blood transfusions.
- Taking too much iron — high-dose iron supplements.
- Some liver conditions and rarer causes.
What does a low Transferrin saturation level mean?
- Iron deficiency — the commonest cause; little iron relative to plenty of empty carrier.
- Anaemia of chronic disease — iron is present in the body but held back, so saturation can be low with a normal or high ferritin.
- Blood loss and increased iron demand — as in heavy periods or pregnancy.
When to discuss with a doctor
Transferrin saturation is interpreted within the iron studies, not alone. A low saturation supports iron deficiency and, with a low ferritin, prompts a search for the cause — dietary, blood loss (including from the gut) or increased demand. A high saturation is an important flag: a persistently raised transferrin saturation is often the first clue to haemochromatosis, which is worth diagnosing because early treatment (simply removing blood periodically) prevents iron building up in the liver, heart and other organs. Because chronic inflammation can distort the individual iron markers, the whole panel is read together. Mediora.AI shows transferrin saturation alongside iron, ferritin and total iron-binding capacity so the iron pattern is read as a set; the interpretation and any treatment belong with your doctor.
Related markers
Commonly confused with
- Transferrin One name, two different numbers. Transferrin is the amount of the iron-carrying protein; the saturation is what percentage of it currently carries iron. Transferrin can be high precisely because iron is low.