Vitamin B12 (named as cobalamin) is considered to be the largest and one of the most complex vitamins of all the vitamin family. It is known to be unique, as it is the only vitamin that consists of a metal ion, named cobalt in its structure (hence its name). Cobalamin, popularly known as vitamin B12 is an important water-soluble vitamin which is involved in the synthesis of red blood cells, neuronal protection and DNA synthesis which are the vital functions of the body.


The 4 Different Forms of B12 have been identified. There are four forms of vitamin B12, mainly differentiated by the side group attached to the cobalamin molecule:

  1. Adenosylcobalamin (AdoCbl)
  2. Cyanocobalamin (CNCbl)
  3. Hydroxocobalamin (HOCbl)
  4. Methylcobalamin (MeCbl)

Methylcobalamin and Adenosylcobalamin are two different co-enzymes and the body requires both of them for different processes. Cyanocobalamin is the most commonly found form in supplements and fortified foods. It is considered to be the most stable form of all the forms of B12 available because of the side group, cyanide, which is believed to be having the strongest attraction to the cobalamin molecule. It is also considered to be stable in extreme conditions like high temperatures compared to other forms. Hydroxocobalamin is the form of B12 commonly found in food. There are not many oral formulations available   for people to take and it is normally injected in B12 shots. It is not recommended to be taken orally as the hydroxyl side group has the least attraction to the cobalamin molecule. Adenosylcobalamin’s chemically known as 5′-deoxy-5′-adenosylcobalamin is also known as dibencozide, cobamamide, and cobinamide.

The main aim of this article, is to state the pros and cons of the two forms of B12 that we are concerned with namely methylcobalamin and cyanocobalamin which are available in the market and are the types that are generally found in supplements and suggest the superiority of methylcobalamin over cyanocobalamin which is used commonly.


Cyanocobalamin a form of vitamin B12 is considered to be a cheap, synthetic, mild toxic and an inactive form of B12. It consists of a cyanide donor in its chemical structure and is the most commonly used commercial preparation of vitamin B12 used. It is considered as the most stable form, because of the cyanide molecule present in the structure has the great attraction to the cobalamin and protects it from extreme conditions like high temperatures. It is not absorbed well orally and requires methyl groups to detoxify it.

The molecule that is attached to the cobalamin is known as a donor. The two most common donors in the available supplements are cyanide (making cyanocobalamin B12, or cyano B12), and methyl (making methylcobalamin B12, or methyl B12). Other forms of B12 we find are hydroxocobalamin and adenosylcobalamin. It’s used more frequently in supplements, since it’s considered to be more stable and cost-effective than all the other forms of vitamin B12 available. When cyanocobalamin enters your body, it is converted to either methylcobalamin or adenosylcobalamin, these are the two active forms of vitamin B12 in humans. When cyanocobalamin is absorbed, it converts to hydroxocobalamin (which means discarding of the cyanide in the process) and then to methylcobalamin and adenosylcobalamin. When taken through oral route, absorption of this form is enormously reduced in case of any gastric acid problems. Besides, cyanocobalmin takes more than 48 hours to eventually convert to usable and active component methylcobalamin, and even then also only a small amount is converted. During this conversion it requires the interaction of possibly depletion of glutathione and other agents.


Unlike cyanocobalamin which is synthetic in nature, methylcobalamin is a naturally occurring form of vitamin B12 which can be obtained through supplements, as well as food sources like fish, meat, eggs and milk. Methylcobalamin is the kingpin, one of the two active, natural forms of B12. It helps in reducing homocysteine concentrations and generates SAMe (S-adenosyl methionine), which is the most important methyl donor in our body, and supplying methyl groups for critical chemical reactions to help maintain our health. Methylcobalamin shows its greatest utility with people suffering from acute or chronic degenerative neurological symptoms, here it is considered as the only promising treatment available. It bypasses several potential issues in the absorption cycle and helps relieve or completely reverse symptoms.

Cyanocobalamin takes a lot of effort to reduce it to the active form; hence cyanocobalamin absorption varies greatly between individuals. Methylcobalamin is considered significantly better utilized compared to other forms and is around 2.5 times more potent (about 1/3 less is excreted in the urine) than cyanocobalamin. Even though similar doses are “absorbed”, but once absorbed, Methylcobalamin due to its high plasma protein binding capacity is accumulated and retained in the body much better than cyanocobalamin therefore the retention time is more. In any form, methylcobalamin has higher bioavailability than cyanocobalamin. It is so efficient that even orally it was found effective in pernicious anemia.


Methylcobalamin Cyanocobalamin
Nature Natural Synthetic
Chemistry active form inactive form, cyanide group, slightly toxic form
Absorption low absorption rate Stable, high absorption rate
Distribution High plasma protein binding Low protein binding
Metabolism Direct active form Converted to methylcobalamin and adenosylcobalamin taking almost 48hrs.

Detoxification required for cyanide group.

Excretion Higher retention time. Can be used in liver and renal toxicity. Not advised in renal or liver toxicity. Eliminated fastly
Safety Safe when compared to other forms Least safe of all forms
Efficacy Good compared to other forms Least efficacious.
Commercial Costly Very cheap


Majority that is 99% of people in the world are in need of extra vitamin B12, and methylcobalamin would be considered as a better option compared to cyanocobalamin. It exhibits many neuroprotective effects, improving brain cognition back to normal levels. Plus, methylcobalamin is donating an extremely valuable methyl group that further enhances our health (and doesn’t steal any, like cyanocobalamin does). This is especially important for pernicious anemia patients or anyone suffering from high homocysteine levels. This donation of methyl groups may be the reason why methylcobalamin is helpful to multiple conditions.