What is Essential Vitamin B12? Essential vitamin B12 is a premium quality supplement containing 1000mg of vitamin B12, a vitamin that plays a key role in a number of functions within the body. Why use Essential Vitamin B12? Vitamin B12 plays an important role in supporting mechanisms within the body in converting food into a usable energy source, contributing to the normal metabolism of energy resulting in reduced tiredness and fatigue. Vitamin B12 also supports normal psychological & nervous functions a