The two types of vitamin B12 shots are cyanocobalamin and methylcobalamin, according to VitaminInjections.net. Cobalamin is the medical term for vitamin B12, and these two compounds are so similar that only one molecule differentiates them. Although small, the difference can affect the health of the individual taking it.
Cyanocobalamin, which has a cyanide molecule attached to the cobalamin compound, is cheaper to produce synthetically than obtaining the naturally occurring form of vitamin B12, methylcobalamin, which has a methyl molecule attached to the cobalamin compound, asserts VitaminInjections.net. Because of this, most supplements are made with cyanocobalamin, but because the body cannot process vitamin B12 with the cyanide molecule, it must remove it and attach a methyl molecule. The human body has a natural resource of methyl molecules used in a process called methylation that stabilizes and aids in the body's natural detoxification.
Taking methylcobalamin replenishes the body's natural supply of methyl, and taking cyanocobalamin depletes it, states VitaminInjections.net. If the methyl supply is depleted too much, it could have negative health consequences. Methylcobalamin can also be processed as-is immediately because it is a pure, natural form of B12. This is particularly true when it is applied with an injection, because it bypasses the absorption process in the small intestine and is carried by the blood to the nervous system or used to make more cells.