Vitamin B12 is one of the 8 B vitamins and is water soluble. It is found bound to protein, where it is used in several metabolic processes, and is important for one-carbon metabolism. One-carbon metabolism is a series of metabolic processes that are crucial for cellular function.[1][2] Vitamin B12 acts as a cofactor in these metabolic processes throughout the body, including the production of methionine, one of the amino acids that is integral for the production of the purines that make up DNA.[2]