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Limited evidenceVitamins & minerals

Adenosylcobalamin

One of the two coenzyme forms of vitamin B12, required by a mitochondrial enzyme. Sold as "mitochondrial B12", but no human trial shows it does anything ordinary B12 does not.

Evidence last reviewed: August 2026

What the science says

  • A genuine, required coenzyme Moderate evidence

    Reviews of B12 biochemistry confirm adenosylcobalamin is the obligatory cofactor for methylmalonyl-CoA mutase, and that without it methylmalonic acid accumulates. This is established biochemistry, not evidence that supplementing this particular form is better.

  • No demonstrated advantage as a supplement Limited evidence

    A review of the cobalamin forms concluded that coenzyme forms are unlikely to be superior to cyano- or hydroxocobalamin for preventing or treating deficiency, since swallowed B12 is stripped and reassembled intracellularly. No randomized trial has compared adenosylcobalamin with another form on any clinical outcome.

Dosage & safety

Studied doseProducts typically supply 1000–3000 µg/day, usually paired with methylcobalamin. No dose has been established in trials — this is a label dose, not a studied one.
SafetyNo specific toxicity is known and there is no upper limit for B12. The same caveat applies as for any B12 product: anemia or neurological symptoms need a diagnosis, not just a supplement. Inherited methylmalonic acidemias are treated with prescription hydroxocobalamin under specialist care, not with supplements.

Scientific references

Where to buy

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