Is it ensure, insure, or assure?
cobalamin co·bal·a·min (kō-bāl'ə-mĭn) or co·bal·a·mine (-mēn')
See vitamin B12.
a complex water-soluble organic compound that is essential to a number of microorganisms and animals, including humans. Vitamin B12 aids in the development of red blood cells in higher animals. The vitamin, which is unique in that it contains a metallic ion, cobalt, has a complex chemical structure as shown: