Moderate evidenceVitamins & minerals

Methylcobalamin

The methylated coenzyme form of vitamin B12. It corrects B12 deficiency reliably, but the common claim that it is better absorbed or better used than cheap cyanocobalamin is not supported by evidence.

Evidence last reviewed: August 2026

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What the science says

Oral B12 corrects deficiency Moderate evidence
A Cochrane review of 3 randomized trials (153 people) found oral B12 around 1000 µg/day normalised serum B12 as well as intramuscular injection, at lower cost. Evidence quality was rated low, mainly because the trials were small and short.
Not shown to beat cyanocobalamin Moderate evidence
A review of cobalamin metabolism concluded that the coenzyme forms (methyl- and adenosylcobalamin) are unlikely to be superior to cyano- or hydroxocobalamin for preventing or treating deficiency, because all absorbed B12 is processed and re-converted inside cells regardless of the form swallowed.
Diabetic nerve symptoms Limited evidence
A 2026 meta-analysis of 13 randomized trials (834 patients) found B vitamins improved some neuropathy screening scores and sural nerve conduction in diabetic peripheral neuropathy, but had no significant effect on pain, with high heterogeneity and mixed risk of bias.

Dosage & safety

Studied dose500–1000 µg/day orally for maintenance; 1000–2000 µg/day when correcting a deficiency. Sublingual and swallowed tablets perform similarly.

SafetyVery well tolerated with no established upper limit; excess is excreted. The important caveat is diagnostic: self-treating anemia or neurological symptoms with B12 can delay finding the cause (pernicious anemia, malabsorption). Metformin and long-term proton-pump inhibitors lower B12 and are common reasons for a genuine deficiency.

Scientific references

Oral vitamin B(12) versus intramuscular vitamin B(12) for vitamin B(12) deficiency
Wang H, Li L, Qin LL — Cochrane Database Syst Rev, 2018
Cobalamin coenzyme forms are not likely to be superior to cyano- and hydroxyl-cobalamin in prevention or treatment of cobalamin deficiency
Obeid R, Fedosov SN, Nexo E — Mol Nutr Food Res, 2015
Vitamin B Supplementation for Diabetic Peripheral Neuropathy: A Review and Meta-Analysis
Mandra EV, Parfenov VA, Stupin VA — J Clin Med, 2026

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