Transferrin
What it measures, and what changes the number.
Transferrin is the main protein that carries iron in the blood, delivering it from the gut and from storage sites to the bone marrow and other tissues. The test measures how much of this carrier protein is present, whether or not it is holding iron.
It is part of an iron panel and is read alongside serum iron, ferritin and transferrin saturation. TIBC measures a closely related quantity, the total iron-binding capacity of the blood, and some labs report transferrin instead of TIBC or calculate one from the other.
Transferrin is made by the liver and can change with inflammation, pregnancy, hormonal contraception and nutritional state, which is why it is usually interpreted together with the other iron markers. Labs may report it as Transferrina.
Often read alongside: Iron, Ferritin, Transferrin saturation, TIBC