Transferrin saturation shows what share of the iron-carrying protein transferrin is actually loaded with iron at the moment of the draw. It is calculated from serum iron and the binding capacity rather than measured directly, and it describes how much iron is available in circulation for the bone marrow and other tissues. Together with ferritin it is one of the two main figures used to describe body iron status.
No readings for this marker yet.
Low saturation most often points at iron deficiency, and it tends to fall before the blood count changes; it can also be low in chronic inflammation, where iron is present but held back from circulation. High saturation most often reflects iron overload, including hereditary haemochromatosis, repeated transfusions or generous iron supplementation. A single value outside the range is a reason to repeat the test and discuss it with a doctor rather than a conclusion in itself.
Serum iron swings through the day and is usually highest in the morning, so the calculated saturation follows that rhythm; an iron tablet or an iron-rich meal shortly before the draw can lift it sharply, and an acute illness pushes it down. It is read alongside ferritin, serum iron, transferrin and total iron binding capacity, since the same saturation figure means different things depending on whether stores are empty or inflammation is masking them.
Reference ranges are general adult values and depend on lab, assay, age and sex. For orientation, not diagnosis — discuss results with your doctor.