Transferrin is a protein produced by the liver that is used to transport iron to the bone marrow, where iron is incorporated into the hemoglobin of red blood cells. The level of transferrin depends on the individual’s nutritional status and proper liver function. Normally, one-third of transferrin binding sites are occupied by an iron atom. The remaining two-thirds are reserve capacity (TIBC or total iron binding capacity). “Iron saturation” provides a measure of the % of transferrin sites occupied by iron. Results of the transferrin levels, TIBC or iron saturation are interpreted in light of other parameters, including serum iron levels, ferritin levels or certain elements in the blood count (red blood cells, hemoglobin, hematocrit, etc.).
High transferrin or TIBC levels with a low saturation % may indicate iron deficiency (iron anemia). A high percentage of transferrin saturation is one of the earliest signs of hemochromatosis or iron poisoning (excess iron in the tissues), but it can also be seen in certain non-iron-deficiency anemias such as hemolytic anemia (rupturing of the red blood cells).