Cobalamin or vitamin B12 is a chemical compound. It is needed for nerve cells and red blood cells, and to make DNA.
It is an organometallic compound with a trivalent cobalt ion bound inside a corrin ring. Its chemical structure was determined by Dorothy Crowfoot Hodgkin.
Vitamin B12 is mostly absorbed in the terminal ileum. The production of intrinsic factor is vital to absorption of this vitamin.
In nature, it is solely produced by bacteria found in animals, and is thus often lacking in those leading a vegetarian diet. However, specialty B12 enriched foodstuffs, usually soya based, are now available.