Transferrin saturation, abbreviated as TSAT and measured as a percentage, is a medical laboratory value. It is the ratio of serum iron and total iron-binding capacity. Of the transferrin that is available to bind iron, this value tells a clinician how much serum iron are actually bound. For instance, a value of 15% means that 15% of iron-binding sites of transferrin are being occupied by iron. For an explanation of some clinical situations in which this ratio is important, see Total iron-binding capacity. The three results are usually reported together.
Laboratories often use different units and "normal" may vary by population and the lab techniques used. Look at the individual laboratory reference values to interpret a specific test (for instance, your own).