Transferrin Saturation
Transferrin saturation is the percentage of your iron-transport capacity that is actually carrying iron, calculated by dividing serum iron by TIBC. It shows how 'full' your iron-carrying seats are.
Because it combines serum iron and TIBC into one ratio, transferrin saturation is often one of the most useful single indicators of iron balance. It helps distinguish between iron deficiency, where saturation tends to be low, and iron overload, where it tends to be high. It's especially valuable when read with ferritin.
A high transferrin saturation can suggest iron overload, including conditions like hemochromatosis, but it doesn't confirm any diagnosis on its own. Recent iron intake and other factors can also raise it. It's interpreted together with ferritin and the rest of the panel.
A low transferrin saturation is a common sign of iron deficiency, indicating that relatively little of your carrying capacity is being used. It's most meaningful alongside ferritin and serum iron.
Reference ranges differ by lab, and the ratio depends on serum iron, which fluctuates through the day. A clinician can explain what your saturation means within your complete iron picture.
Sources
Educational context only, not medical advice or a diagnosis. Reference ranges vary by lab, age and sex; always discuss your results with a clinician.
Associations to explore with a clinician, not a diagnosis from a single number.