Transferrin is the main protein in the blood that binds to iron and transports it throughout the body. Transferrin levels rise with iron deficiency and fall in cases of iron overload. Transferrin is also responsible for circadian variation in serum iron (which peaks in the AM).

Normally, iron is absorbed from food and transported throughout the body by transferrin, which is produced by the liver. About 70% of the iron is transported to the bone marrow and incorporated into hemoglobin within red blood cells. The remainder is stored in the tissues as ferritin.

An 8 to 12 hour fast is required for this blood test. However, drink plenty of water and take medications as prescribed.