Transferrin Saturation

Transferrin saturation is the percentage of iron-binding sites on transferrin that are currently carrying iron. It is calculated as (serum iron ÷ TIBC) × 100 and is reported as part of standard iron studies in Australia. Of the four iron-studies markers, transferrin saturation is the most sensitive single test for haemochromatosis screening.

Transferrin saturation gives a real-time picture of iron in transit, complementing ferritin (stored iron). It is the recommended first-line screening test for hereditary haemochromatosis in Australia: a fasting morning saturation persistently >45% (men) or >40% (women) is the threshold to proceed to HFE genetic testing. Low saturation supports a diagnosis of iron deficiency, while high saturation can also occur in liver disease, frequent blood transfusions, and after recent iron supplementation.

Persistently high transferrin saturation (>45% in men, >40% in women) is the most sensitive marker for hereditary haemochromatosis (HFE gene mutation), affecting roughly 1 in 200 Australians of Northern European descent. Other causes include iron supplementation taken on the morning of the test, frequent blood transfusions (e.g. for thalassaemia), acute hepatitis, and iron overload from chronic alcohol use. Repeat testing on a fasting morning sample without iron supplements is essential before ordering HFE genetic testing.

Low transferrin saturation indicates inadequate iron supply for transport, most commonly due to iron-deficiency anaemia, anaemia of chronic disease, blood loss (heavy menstruation, GI bleeding) or pregnancy. The four-marker iron studies pattern distinguishes the cause: low saturation + low ferritin + high TIBC = iron deficiency. Low saturation + normal/high ferritin + low TIBC = anaemia of chronic disease.

Reported on every iron studies panel. Annually for screening, every 3 months while treating iron deficiency, every 6–12 months for haemochromatosis surveillance.

Always interpreted alongside ferritin, serum iron and TIBC. For haemochromatosis screening, persistently elevated saturation triggers HFE genetic testing.