The Intrinsic Factor Antibodies blood test is used to investigate the cause of vitamin B12 deficiency, particularly when pernicious anaemia is suspected. Intrinsic factor is a specialised protein produced by the stomach lining that is essential for the absorption of vitamin B12 in the small intestine.

Vitamin B12 plays a critical role in red blood cell production, neurological function, and DNA synthesis. When B12 levels are low, individuals may experience symptoms such as fatigue, weakness, shortness of breath, memory difficulties, mood changes, or tingling and numbness in the hands and feet.

In pernicious anaemia, the immune system mistakenly produces antibodies that attack intrinsic factor. These antibodies prevent vitamin B12 from binding to intrinsic factor, meaning it cannot be absorbed properly, even if dietary intake of B12 is adequate.

This autoimmune process leads to progressive vitamin B12 deficiency over time. Because the condition develops slowly, symptoms may be subtle at first and are sometimes mistaken for stress, ageing, or other health issues.

The Intrinsic Factor Antibodies test is most commonly requested when blood tests show low vitamin B12 levels, macrocytic anaemia, or when neurological symptoms are present without a clear dietary explanation. It is often performed alongside parietal cell antibody testing and other investigations to build a complete diagnostic picture.

Identifying intrinsic factor antibodies is important because pernicious anaemia requires lifelong management. Standard oral vitamin B12 supplements are often ineffective, and treatment usually involves regular vitamin B12 injections or high-dose oral therapy under medical supervision.