Intrinsic factor is a natural substance normally found in the stomach. You need this substance to absorb vitamin B12 from foods.

A lack of intrinsic factor leads to pernicious anemia and vitamin B12 deficiency, which can cause anemia and brain and nervous system (neurological) problems.

Intrinsic factor - lack of

Babies that are born without intrinsic factor cannot properly absorb vitamin B12 starting around age 6 months. Children who have the juvenile type of lack of intrinsic factor tend to show signs and symptoms after age 10.

Older adults get pernicious anemia, which is caused by a lack of intrinsic factor production. This is usually due to an autoimmune disease that causes the stomach lining to waste away (atrophy). The stomach lining is where intrinsic factor is usually made.

Antony AC. Megaloblastic anemias. In: Hoffman R, Benz EJ, Shattil SS, et al., eds. Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone; 2008:chap 39.