Test Details: A transferrin test is carried out to directly measure the level of iron in the blood and also the body's ability to transport iron in the blood. The transferrin blood test is ordered on suspicion of abnormalities in iron levels of body. The tests help diagnose chronic iron overload or deficiency. Transferrin saturation levels cannot be interpreted alone. They are used in conjunction with other laboratory tests, such as serum ferritin and TIBC.