What causes high vitamin b12 levels?

Intake + Absorption: Vitamin b12, aka cyanocobalamin, is common in a huge variety of foods; low intake rare. However, none of us absorb B12 directly. Instead, the cells of the upper ⅔ of the stomach which secrete hydrochloric, hcl, acid also produce & secrete a protein, called intrinsic-factor, which binds b12. The small intestines absorb intrinsic-factor with whatever B12 is bound, & the B12 is thereby also absorbed.