Why would ihave low vitamin b12?

Possible causes: You could have a low b-12 if you are vegetarian, have been for several years and don't take supplemental b-12. It could be low if you don't make intrinsic factor. This is made in the stomach and is needed to absorb b-12. Lack of intrinsic factor is usually an autoimmune disorder. You could have low b-12 due to taking proton pump inhibitors for a long time as stomach acid is needed as well.

Are you taking: Medicine for gerd? Proton inhibitors can cause low B12 levels in some people- pernicious anemia patients have low levels this problem should be followed up ; treated by your pcp.