Vitamin B12 as Methylcobalamin is a tissue-ready form of vitamin B12. Methylcobalamin is essential for the body to recycle homocysteine and to form the internal methyl donors involved in cardiovascular function, sleep, blood cell formation, and nerve function.* Most vitamin B12 supplements contain cyanocobalamin; however, the liver must first “detoxify” the cyanide molecule in cyanocobalamin and then attach a methyl group to form methylcobalamin.