Intrinsic Factor is a protein produced by human parietal cells located in the stomach and digestive tract. Intrinsic Factor is responsible for transporting Vitamin B12 from the digestive tract into the bloodstream. Health conditions or genetic factors impacting Intrinsic Factor production are likely to have an immediate impact on B12 absorption resulting in a deficiency.

Intrinsic Factor is out-competed for binding to B12 compounds in the stomach but later binds in the lower intestines. The lining of the digestive tract has Intrinsic Factor receptors through which the Intrinsic Factor bound b12 is absorbed into the bloodstream.