Transferrin is tested to essentially learn about the body’s iron stores. TIBC or transferrin are typically used along with iron and ferritin to evaluate people suspected of having too much or too little iron stored within their body. Usually, about one third of the transferrin measured is being used to transport iron, and this is called transferrin saturation. In iron deficiency, iron is low and fewer transferrin binding sites are used. This results in a low transferrin saturation, but an increased TIBC. In iron overload, iron and transferrin saturation will be high and TIBC will be low or normal.

Because transferrin is made in the liver, TIBC and transferrin will also be low with liver disease.