Also Known As
IF Antibody
IF Antibody Type 1 or Type 2
Intrinsic Factor Binding Antibody
Intrinsic Factor Blocking Antibody
Anti-Intrinsic Factor
Formal Name
Intrinsic Factor Antibody
This article was last reviewed on
This article waslast modified on November 5, 2017.
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 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 healthcare providers may prefer not to draw a blood sample for the test within 2 weeks of an injection.

You may be able to find your test results on your laboratory's website or patient portal. However, you are currently at Lab Tests Online. You may have been directed here by your lab's website in order to provide you with background information about the test(s) you had performed. You will need to return to your lab's website or portal, or contact your healthcare practitioner in order to obtain your test results.

Lab Tests Online is an award-winning patient education website offering information on laboratory tests. The content on the site, which has been reviewed by laboratory scientists and other medical professionals, provides general explanations of what results might mean for each test listed on the site, such as what a high or low value might suggest to your healthcare practitioner about your health or medical condition.

The reference ranges for your tests can be found on your laboratory report. They are typically found to the right of your results.

If you do not have your lab report, consult your healthcare provider or the laboratory that performed the test(s) to obtain the reference range.

Laboratory test results are not meaningful by themselves. Their meaning comes from comparison to reference ranges. Reference ranges are the values expected for a healthy person. They are sometimes called "normal" values. By comparing your test results with reference values, you and your healthcare provider can see if any of your test results fall outside the range of expected values. Values that are outside expected ranges can provide clues to help identify possible conditions or diseases.

While accuracy of laboratory testing has significantly evolved over the past few decades, some lab-to-lab variability can occur due to differences in testing equipment, chemical reagents, and techniques. This is a reason why so few reference ranges are provided on this site. It is important to know that you must use the range supplied by the laboratory that performed your test to evaluate whether your results are "within normal limits."

For more information, please read the article Reference Ranges and What They Mean.

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 (neutropenia, thrombocytopenia) 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.

For more on these, see the next tab, "The Test."

How is the sample collected for testing?

A blood sample is obtained by inserting a needle into a vein of the arm.

Is any test preparation needed to ensure the quality of the sample?

If you receive a vitamin B12 injection, you should wait 48 hours before having your blood drawn to reduce the risk of having a false-positive test result. Some healthcare providers may prefer not to draw a blood sample for the test within 2 weeks of an injection.

Accordion Title
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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Osborne, D., & Sobczynska-Malefora, A. (2015). Autoimmune mechanisms in pernicious anaemia & thyroid disease. Autoimmun Rev, 14(9), 763-768. doi: 10.1016/j.autrev.2015.04.011.

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(September 2, 2015.) Schrier, SL. Diagnosis and treatment of vitamin B12 and folate deficiency. In: UpToDate, Timauer JS (Ed). UpToDate, Waltham, MA. Available online through http://www.uptodate.com. Accessed on September 2, 2015.

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