Many vitamin B12 supplements contain cyanocobalamin as the active ingredient, which the liver must first "detoxify" and modify to form methylcobalamin – an active form of vitamin B12 that is essential for processes involved in cardiac function, sleep, blood cell formation, and nerve function. Thorne's Vitamin B12, as Methylcobalamin, provides vitamin B12 in its already biologically active and tissue-ready form. Clinical evidence indicates that the body uses methylcobalamin more efficiently than cyanocobalamin. Methylcoblamin helps maintain normal circadian rhythms to promote normal sleep and supports healthy methylation processes in the body.

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.

Although research shows the quantity of cobalamin detected following an oral dose of methylcobalamin is similar to the amount following administration of cyanocobalamin, significantly more cobalamin accumulates in liver tissue following administration of methylcobalamin. And the urinary excretion of methylcobalamin is about one-third that of a similar dose of cyanocobalamin, indicating substantially greater tissue retention of the former.