Serum transferrin is a transport protein for serum iron. The degree of its saturation by iron varies with different disorders involving iron metabolism.


transferrin saturation in percent =

= (((serum iron in µg/dL) / (total iron binding capacity in µg/dL)) * 100)



• The units for serum iron and TIBC need to be the same. Conventional units are µg/dL. SIU are µmol/L.


Since (see next section):


calculated TIBC (in µg/dL) =

= 1.43 * (transferrin, in mg/dL)


This can be re-written as:


transferrin saturation in percent =

= 69.93 * (serum iron in µg/dL) / (serum transferrin in mg/dL)



• 69.93 = 100 / 1.43

• According to Wu 1 mg of transferrin can bind 1.25 µg of iron rather than 1.43.



• lower limit of normal: greater than or equal to 16% (another source says 20%)

• upper limit of normal: 55%


Transferrin saturation is increased in conditions with iron overload:

(1) hemochromatosis

(2) hemosiderosis

(3) thalassemia


Transferrin saturation is decreased in:

(1) iron deficiency anemia

(2) anemia of chronic disease


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