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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.

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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.

How to take it

TimingTiming does not matter.
With food?With or without food.
Worth knowingThere is no human evidence that adenosylcobalamin does anything methylcobalamin or plain cyanocobalamin does not, at several times the price.

Interactions

With medications

  • metformin

    Long-term metformin lowers B12 absorption. have B12 checked periodically

  • proton-pump inhibitors and H2 blockers

    Reduced stomach acid impairs B12 release from food. have B12 checked if you take them long term

With other supplements

  • high-dose folic acid or folate

    Folate can mask the anemia of B12 deficiency while neurological damage progresses. check B12 status before taking high-dose folate

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

What is adenosylcobalamin and is it mitochondrial B12?

Adenosylcobalamin is a genuine coenzyme form of B12 required by a mitochondrial enzyme, methylmalonyl-CoA mutase. That biochemistry does not mean supplementing this form does anything ordinary B12 does not.

Is adenosylcobalamin better than methylcobalamin or cyanocobalamin?

No human trial shows it: swallowed B12 is stripped and reassembled inside cells, and no randomized trial has compared adenosylcobalamin with another form on any outcome. The evidence for an advantage is limited, and it costs several times more.

How much adenosylcobalamin should I take?

Adenosylcobalamin products typically supply 1000–3000 mcg/day, often paired with methylcobalamin, but this is a label dose rather than a studied one. B12 has no known upper limit.

Is adenosylcobalamin safe?

Adenosylcobalamin has no known specific toxicity. Anaemia or neurological symptoms still need a diagnosis rather than a supplement, and high-dose folate can mask B12 deficiency, so check B12 status first.

Scientific references

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