DefinitionIntrinsic factor is a protein produced by cells in the stomach lining. It is needed for the intestines to absorb vitamin B12efficiently.InformationIn a disease called pernicious anemia, immune system damage to the stomach lining can cause a lack (deficiency) of intrinsic factor. Pernicious anemia causes vitamin B12 deficiency, which leads to a low red blood cell count (anemia).Intrinsic factor deficiencies can also be caused by other reasons, such as:Inherited conditionsOther diseasesSurgical removal of the stomachReferencesAntony AC. Megaloblastic anemia. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 170.Antony AC. Megaloblastic anemia. In: Hoffman R, Benz EJ, Shattil SS, et al., eds. Hematology: Basic Principles and Prac