Vitamin B12, also known as cobalamin, is an essential water-soluble vitamin that plays a critical role in various bodily functions. It is unique among vitamins as it contains the metal ion cobalt, which is why compounds with vitamin B12 activity are collectively called cobalamins. Vitamin B12 is necessary for the proper formation of red blood cells, neurological function, and DNA synthesis. The human body cannot produce vitamin B12, so it must be obtained through diet or supplements.