Test Catalog

Test ID: FEC    
Iron and Total Iron-Binding Capacity, Serum

Useful For Suggests clinical disorders or settings where the test may be helpful

Screening for chronic iron overload diseases, particularly hereditary hemochromatosis

Testing Algorithm Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

See Hereditary Hemochromatosis Algorithm in Special Instructions.

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Ingested iron is absorbed primarily from the intestinal tract and is temporarily stored in the mucosal cells as ferritin (Fe[III]). Ferritin provides a soluble protein shell to encapsulate a complex of insoluble ferric hydroxide-ferric phosphate. On demand, iron is released into the blood by mechanisms that are not clearly understood, to be transported as Fe(III)-transferrin.


Transferrin is the primary plasma iron transport protein, which binds iron strongly at physiological pH. Transferrin is generally only 25% to 30% saturated with iron. The additional amount of iron that can be bound is the unsaturated iron-binding capacity (UIBC). The total iron-binding capacity (TIBC) can be indirectly determined using the sum of the serum iron and UIBC. Knowing the molecular weight of the transferrin and that each molecule of transferrin can bind 2 atoms of iron, TIBC and transferrin concentration is interconvertible.


Percent saturation (100 x serum iron/TIBC) is usually normal or decreased in persons who are iron deficient, pregnant, or are taking oral contraceptive medications. Persons with chronic inflammatory processes, hemochromatosis, or malignancies generally display low transferrin.


Serum iron, total iron-binding capacity, and percent saturation are widely used for the diagnosis of iron deficiency. However, serum ferritin is a much more sensitive and reliable test for demonstration of iron deficiency.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.


Males: 50-150 mcg/dL

Females: 35-145 mcg/dL



250-400 mcg/dL




Interpretation Provides information to assist in interpretation of the test results

In hereditary hemochromatosis, serum iron is usually above 150 mcg/dL and percent saturation is above 60%. In advanced iron overload states, the percent saturation often is above 90%.


For more information about hereditary hemochromatosis testing, see Hereditary Hemochromatosis Algorithm in Special Instructions.

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Measurement of serum iron, iron-binding capacity, and percent saturation should not be used as a test for iron deficiency. It is often unreliable for this purpose.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Tietz Textbook of Clinical Chemistry. Edited by CA Burtis, ER Ashwood. Philadelphia, WB Saunders Company. 1999

2. Fairbanks VF, Baldus WP: Iron overload. In Hematology. Fourth edition. Edited by WJ Williams, AJ Erslev, MA Lichtman. New York, McGraw-Hill Book Company, 1990, pp 482-505

Special Instructions Library of PDFs including pertinent information and forms related to the test