Reference values — Total Iron-Binding Capacity (TIBC)

Total iron-binding capacity reflects the amount of iron that can be bound by serum transferrin. Pregnancy increases transferrin and TIBC as maternal iron requirements rise and plasma volume expands.

Units Nonpregnant adult First trimester Second trimester Third trimester
µg/dL 228 – 428 235 – 408 302 – 519 380 – 597
µmol/L 40.8 – 76.7 42 – 73 54 – 93 68 – 107
Total iron-binding capacity (TIBC), serum. Values reflect typical ranges in pregnancy and may vary slightly between laboratories.
Pregnancy physiology and TIBC
  • Estrogen and increased hepatic protein synthesis lead to a rise in transferrin, the main iron-transport protein.
  • As transferrin increases, TIBC increases, especially in the second and third trimesters.
  • Plasma volume expansion and increased iron demand (maternal erythropoiesis and fetal–placental needs) further contribute to increased TIBC.
  • TIBC is typically interpreted together with serum iron and transferrin saturation when evaluating iron deficiency or iron overload.
Causes of elevated TIBC

Elevated TIBC usually reflects increased circulating transferrin, most often in the setting of iron deficiency or increased iron demand.

  • Iron deficiency (with or without anemia)
  • Pregnancy and lactation (increased iron requirements)
  • Acute or chronic blood loss with developing iron deficiency
  • Estrogen therapy or oral contraceptives (increased transferrin production)
  • Post–iron-deficiency recovery phase
  • Some chronic liver diseases with preserved synthetic capacity and increased transferrin
Causes of low TIBC

Decreased TIBC typically indicates reduced transferrin production or loss of transferrin, or reflects states of iron overload.

  • Anemia of chronic disease / inflammation
  • Iron overload (hemochromatosis, multiple transfusions)
  • Chronic liver disease with impaired protein synthesis
  • Nephrotic syndrome and other protein-losing states
  • Malnutrition or severe hypoproteinemia
  • Acute infection or systemic inflammatory states
References

Key sources

  1. Lockitch G. Handbook of Diagnostic Biochemistry and Hematology in Normal Pregnancy. Boca Raton: CRC Press; 1993.
  2. Kratz A, Ferraro M, Sluss PM, Lewandrowski KB. Laboratory reference values. N Engl J Med. 2004;351(15):1548–1563. PMID: 15470219
  3. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114(6):1326–1331. PMID: 19935037
  4. Fischbach FT, Dunning MB III, eds. Manual of Laboratory and Diagnostic Tests. 7th ed. Philadelphia: Lippincott Williams & Wilkins; 2004.