Why vitamin B-12 may not get absorbed.
Pernicious anemia is the most common cause.
The name dates back many years to the time when there was no treatment for this type of anemia. Persons with it would become increasingly ill and die, often with severe neurological complications. It is now easily treated with injections of vitamin B-12, which are inexpensive and have no harmful side effects. Antibodies against the intrinsic factor itself may also be present. People who can't make enough intrinsic factor can't absorb vitamin B-12 from the gastrointestinal tract.