Intrinsic factor

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Intrinsic factor is a protein that helps your intestines absorb vitamin B12. It is made by cells in the stomach lining.


Intrinsic factor is a protein that helps your body absorb vitamin B12. Vitamin B12 is needed for red blood cells to form and grow.

Some people do not make enough intrinsic factor or have a condition that destroys it. If your body does not make enough intrinsic factor, you can develop a type of vitamin B12 deficiency called pernicious anemia.

Surgical removal of the stomach and certain other health conditions can also cause you to stop making intrinsic factor.


Antony AC. Megaloblastic anemia. In: Hoffman R, Benz EJ Jr, Silberstein LE, Heslop HE, Weitz JI, Anastasi J, eds. Hematology: Basic Principles and Practice. 6th ed. Philadelphia, PA: Elsevier; 2013:chap 37.

Antony AC. Megaloblastic anemias. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 164.

Version Info

  • Last reviewed on 2/12/2016
  • Todd Gersten, MD, Hematology/Oncology, Florida Cancer Specialists & Research Institute, Wellington, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.

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