A method and composition for treating vitamin B12 deficiency in mammals thatfail to respond to oral vitamin B12 therapy, including preparing a pharmaceuticalcomposition for oral administration containing vitamin B12 and at least onesubstance selected from the group consisting of N-[8-(2-hydroxybenzoyl) amιno]caprylιcacid and its pharmaceutically acceptable salts, then administering the pharmaceuticalcomposition to a subject to effectively treat the vitamin B12 deficiency.