Methylcobalamin vs cyanocobalamin
Methylcobalamin is not a proven upgrade over cyanocobalamin for preventing or treating B12 deficiency. A review of the coenzyme forms reached that conclusion directly. What matters is whether you absorb B12 at all, especially after 50, on metformin, or on a vegan diet, and whether the dose is oral and high enough or given by injection. A pretty form on the label does not fix an absorption problem.
Supplement aisles price methylcobalamin above cyanocobalamin and call it the active form. Vitamin B12 chemistry is real. The clinical ranking is less dramatic.
The comparison that exists
Obeid and colleagues reviewed the coenzyme forms and concluded they are not likely to be superior to cyano- and hydroxocobalamin for preventing or treating deficiency (PMID 25820384). "Active" on a label is not a trial result. People who cannot absorb B12 from food, including many older adults and people with pernicious anemia, need a route and a dose that bypass the missing step. That is a clinician's decision, often an injection or a defined high oral dose, not a form upgrade.
Who should actually supplement
Vegan diets do not contain reliable B12. Metformin and long-term acid-suppressing drugs are common reasons a level falls. A multivitamin amount can be enough for prevention in someone who absorbs normally. It can be nowhere near enough for treatment of a deficiency. Test, do not guess, if there are neurologic symptoms.
Sources
- Obeid R, et al. Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency. Mol Nutr Food Res. 2015. PMID: 25820384.