It makes no difference for synthesis of active cobalamin whether you first ingest it as Cyanocobalamin or Methylcobalamin. The active form of Methylcobalamin is synthetized with the use of methyl groups donated from folate or SAMe, not from ingested Methylcobalamin.
Methylcobalamin is often marketed as more bio-available and more readily absorbed than Cyanocobalamin. When used intravenously that might be the case. Yet, when it comes to taking it orally, the evidence does not suggest any significant difference in absorption. The same is true between the sublingual and oral route.
Cyanocobalamin is synthethised in the laboratories. For that reason it is often referred to as a synthetic form of B12.
There are three ways to obtain Methylcobalamin:
It is often referred to as being a more natural product. Yet, as you can see, if it is non-GMO and vegan, its manufacturing process is in fact similar to that of cyanocobalamin.
The medical profession has used cyanocobalamin for years now – both in supplement and injection form.
There are many studies confirming its safety and effectiveness. Yes, it contains cyanide molecule which separates from the cobalamin and is excreted in your urine. Note though that each 1000mcg cyanocobalamin tablet contains only 20 micrograms of cyanide. This is far less than you consume in almonds, millet sprouts, lima beans, soy, spinach, bamboo shoots, or tapioca. Should you accidentally chewed one apple pip you’ll swallow roughly 490 milligrams of cyanide. That’s almost twenty-five times more than one 1000mcg cyanocobalamin tablet.
Currently, there is not enough evidence to suggest that the benefits of using methylcobalamin override that of using cyanocobalamin. This is in terms of bioavailability, biochemical effects, or clinical efficacy. Yet, if you have kidney issues (which can affect cyanide elimination) methylcobalamin may be a better choice for you. In all other cases cyanocobalamin will work as well.