Intrinsic Factor Antibody
- Also Known As:
- IF Antibody
- IF Antibody Type 1 or Type 2
- Intrinsic Factor Binding Antibody
- Intrinsic Factor Blocking Antibody
- Anti-Intrinsic Factor

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At a Glance
Why Get Tested?
To help diagnose pernicious anemia, the most common cause of vitamin B12 deficiency
When To Get Tested?
As part of an investigation, when you have anemia and/or neuropathy, which is numbness, tingling, pain and weakness in the affected area that may be due to a vitamin B12 deficiency; when you have red blood cells that are much larger than normal (macrocytic)
Sample Required?
A blood sample drawn from a vein in your arm
Test Preparation Needed?
You should wait at least 48 hours after receiving a vitamin B12 injection to have a blood sample taken. Some health care providers may prefer not to draw a blood sample for the test within 2 weeks of an injection.
What is being tested?
Intrinsic factor antibodies are proteins produced by the immune system that are associated with pernicious anemia. This test detects intrinsic factor antibody (IF antibody) circulating in blood.
Intrinsic factor is a protein produced by a type of specialized cells that line the stomach wall known as parietal cells. During digestion, stomach acids release vitamin B12 from food and bind to intrinsic factor to form a complex. The formation of this complex is necessary for the absorption of vitamin B12 in the small intestine.
Among having functional roles in the brain and nervous system, vitamin B12 is important in the production of red blood cells. Without sufficient intrinsic factor, vitamin B12 goes largely unabsorbed and the body cannot produce enough normal red blood cells, leading to anemia. Besides anemia, decrease in the numbers of neutrophils and platelets may also occur.
Anemia that is due to a lack of intrinsic factor is called pernicious anemia. This is primarily an autoimmune condition that occurs when the body’s immune system targets its own tissues and develops antibodies directed against the parietal cells and/or the intrinsic factor. These antibodies can damage the parietal cells and disrupt intrinsic factor production or prevent intrinsic factor from carrying out its biological function.
Two types of IF antibodies can be tested by the laboratory:
- Intrinsic factor blocking antibody (type 1), which is more specific for pernicious anemia and is the one that is usually tested.
- Intrinsic factor binding antibody (type 2), which interferes with the uptake of the vitamin B12-instrinsic factor complex.
Common Questions
View Sources
Sources Used in Current Review
2015 review performed by Boris Calderon, MD, DABCC, FACB, Staff Scientist, Clinical Center NIH.
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