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evidence · mechanism · dose
Supplements/Vitamin

Methylcobalamin (B12)

Active methyl-form of B12 — directly usable in the methylation cycle.

Energy ProductionBrain & CognitiveMood & Anxiety

Overview

Active methyl-form of B12 — directly usable in the methylation cycle.

Natural sources
    Common forms

      Forms & variants of Vitamin B12

      Different chemical forms of Vitamin B12 behave differently. Browse each form's mechanism, bioavailability, and best-use context.

      Parent
      Vitamin B12

      Essential cobalamin for methylation, red blood cell formation, and myelin maintenance.

      Adenosylcobalamin
      Adenosylcobalamin (B12)

      Mitochondrial coenzyme form of B12 — partners with methylcobalamin for full B12 status.

      Hydroxocobalamin
      Hydroxocobalamin (B12)

      Long-acting injectable form of B12 — used clinically for deficiency and cyanide poisoning.

      Mechanism of action

      Donates methyl group to homocysteine via methionine synthase; no liver conversion needed.

      Pathways
      • · Methionine synthase
      • · Methylation cycle

      Effects on the body

      Organ system effects

      Evidence-based benefits

      Repletes B12 in deficiency

      Strong evidence

      Possible benefit in diabetic neuropathy

      Limited evidence

      Potential side effects

      Common
        Rare
          Serious

            Drug interactions

            No notable interactions reported.

            Supplement interactions

            Pairs well with

            None listed.

            Avoid combining with

            No specific avoidances listed.

            Dosing & bioavailability

            Typical dose
            500–1000 mcg sublingual
            Study range
            1–5 mg
            Timing
            Morning

            Where to buy

            Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

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            Vitamin
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            Thorne
            Practitioner-grade · NSF tested

            Scientific evidence (9)

            RCTActa Neurol Taiwan · 2005

            Methylcobalamin for diabetic neuropathy

            Sun Y, et al.

            RCT of methylcobalamin in diabetic neuropathy.

            Key findings

            Improved nerve conduction and symptoms.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — Repletes B12 in deficiency

            Live PubMed search

            Live results for "Methylcobalamin (B12) Repletes B12 in deficiency" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "Repletes B12 in deficiency". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — Possible benefit in diabetic neuropathy

            Live PubMed search

            Live results for "Methylcobalamin (B12) Possible benefit in diabetic neuropathy" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "Possible benefit in diabetic neuropathy". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — randomized controlled trial

            Live PubMed search

            Live results for "Methylcobalamin (B12) randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — meta-analysis

            Live PubMed search

            Live results for "Methylcobalamin (B12) meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — pharmacokinetics

            Live PubMed search

            Live results for "Methylcobalamin (B12) pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — safety adverse events

            Live PubMed search

            Live results for "Methylcobalamin (B12) safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewPubMed (NLM) · 1970

            PubMed: Methylcobalamin (B12) — dose response

            Live PubMed search

            Live results for "Methylcobalamin (B12) dose response" across the PubMed/MEDLINE peer-reviewed index.

            Key findings

            Opens current human and preclinical literature matching Methylcobalamin (B12) and "dose response". Filter by RCT, meta-analysis, or year on the results page.

            Open study
            Systematic reviewGoogle Scholar · 1970

            Google Scholar: Methylcobalamin (B12) — clinical evidence

            Live Scholar search

            Cross-database citation index for Methylcobalamin (B12) as it relates to "clinical evidence".

            Key findings

            Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

            Open study
            Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.