TIBC is typically measured along with serum iron to evaluate people suspected of having either iron deficiency or iron overload. The iron concentration divided by TIBC gives the transferrin saturation, which is a more useful indicator of iron status than iron or TIBC alone. In healthy people, about 20-50% of available sites in transferrin are used to transport iron. In iron deficiency, iron is low, but TIBC is increased, and transferrin saturation becomes very low. In iron overload states such as hemochromatosis, iron will be high and TIBC will be low or normal, causing the transferrin saturation to increase.

It is customary to test for transferrin (instead of TIBC) when evaluating a patient's nutritional status or liver function. Because it is made in the liver, transferrin will be low with liver disease. Transferrin levels also drop when there is not enough protein in the diet, so this test can be used to monitor nutrition.

TIBC may be ordered along with serum iron when it appears that you have too much or too little iron in your system. If you have anemia, especially if the red cells are microcytic and hypochromic, iron tests are usually performed. If your doctor suspects that you may have too much iron, or if you have a family history of hemochromatosis, iron and TIBC may be used to see if further testing is needed.

A high TIBC or transferrin usually indicates iron deficiency, but it is also increased in pregnancy and with use of oral contraceptives. A low TIBC or transferrin may occur if you have hemochromatosis, certain types of anemia in which iron accumulates, malnutrition, inflammation, liver disease, or nephrotic syndrome (a kidney disease that causes loss of protein in urine).