Cyanocobalamin — Frequently Asked Questions

Because the cyanide ligand is deliberately introduced to stabilise the molecule. It occupies the sixth coordination position on the cobalt and makes the vitamin markedly more resistant to light, heat and oxidation than the naturally occurring forms, which is what makes it practical to manufacture, store and formulate. The quantity is trace and is released and excreted on conversion.

Not directly. It is a provitamin form: the body must remove the cyanide ligand and convert it to methylcobalamin or adenosylcobalamin before it can function in methionine synthesis or in methylmalonyl-CoA metabolism. For most people that conversion is efficient, which is why cyanocobalamin remains the reference form for supplementation and fortification.

Because of stability and cost. The active coenzyme forms are considerably more light-sensitive and more expensive to produce and handle. Cyanocobalamin withstands processing, formulation and shelf life far better, which matters in food fortification and multivitamin tablets where the vitamin must survive a long and uncontrolled supply chain.

By bacterial fermentation, since the corrin ring structure is far too complex to synthesise economically. The fermentation produces cobalamin forms which are then converted to the cyano form for stability. This is one of the few vitamins for which no practical total chemical synthesis route exists at commercial scale.