What are the different forms of vitamin B12?


CobalaminOver the years, people have asked me about the differences between the available supplemental forms of vitamin B12. What are they? Do they occur in nature or are they made in a laboratory? Do some forms work “better” than others?

The scientific name for vitamin B12, cobalamin, is derived from the element cobalt found at the center of the vitamin B12 molecule. There are several different forms of vitamin B12, each named for the chemical group attached to cobalt, including hydroxocobalamin, methylcobalamin, cyanocobalamin, and adenosylcobalamin. I have seen these forms of B12 available as individual supplements or in multivitamin formulas.



Hydroxocobalamin is a naturally-occurring form of vitamin B12, as it is made by certain bacteria including some strains that live in soil. Not all types of bacteria make vitamin B12 and not all soil contains B12 producing bacteria. Yeast, mushrooms and other types of fungus do not produce vitamin B12, neither do animals nor plants.

Hydroxocobalamin is NOT active in the human body; it requires conversion to a human bioactive form. Hydroxocobalamin has an –OH (hydroxy) group attached to cobalt in the center of the vitamin B12 molecule. To activate this form of B12, the human body removes the –OH group and replaces it with, for example, a methyl (–CH3) group to create the human bioactive form of vitamin B12, methylcobalamin.



Methylcobalamin is a form of vitamin B12 that is involved in methylation reactions in the human body. Another of my videos covers the importance of methylation and the role played by this form of vitamin B12, so I would encourage you to view it for further explanation. Dr. Rick and I have used methylcobalamin for many years and find it to be a reliable form of B12 for our needs. We especially like this form of vitamin B12 because it is a human bioactive form and does not require conversion.



Cyanocobalamin is a synthetic form of B12 made exclusively in a laboratory. It is not a human bioactive form of vitamin B12 and is not made by bacteria in nature. Cyanocobalamin has a –CN (cyano) group attached to cobalt in the center of the vitamin B12 molecule. Many people have expressed concern about this cyano group as being problematic or toxic, but I have yet to see research or clinical data indicating the use of cyanocobalamin as being associated with these types of issues. When one expresses concern to me, I suggest the use of another supplemental form. As mentioned earlier, I have been using methylcobalamin for many years with good results. If someone is not getting the results they want from their vitamin B12 supplement, clinically or otherwise, I suggest that they contact a qualified healthcare provider to help them find the solution that works best for them.

Despite this controversy, cyanocobalamin is one of the most popular supplemental forms of vitamin B12 because of its stability and shelf-life. For example, cyanocobalamin has a longer shelf-life than methylcobalamin, so supplement manufacturers like to produce and sell it. Since cyanocobalamin is not human bioactive, our body must convert it to one of the human bioactive forms. In which case, the body must remove the –CN group and replace it with either a methyl group or an adenosyl group.



Like methylcobalamin, adenosylcobalamin is one of the human bioactive forms of vitamin B12. This is the form of vitamin B12 that can be stored by our body, specifically in our liver. All previously discussed forms of B12 can be converted into adenosylcabalamin for storage, when our body has more vitamin B12 than is needed for body function.

Adenosylcobalamin is also very important for energy-producing reactions in the human body, as are various other B vitamins. Additionally, adenosylcobalamin is responsible for keeping methylmalonic acid levels appropriately low in the human body. I have a recent video and article describing the significance of methylmalonic acid and its conversion by adenosylcobalamin in the human body, and would encourage you to view it for more information.

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