Educational dose math only — not medical advice, not a product recommendation, and not a pass/fail on whether a supplement will work for you.
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1000 mcg/day oral methylcobalamin for a year normalised B12 and improved nerve conduction in metformin-treated diabetic neuropathy; the Cochrane review found oral matches intramuscular for correcting levels. After labs, with clinician oversight.

Educational only — not medical advice. Disclaimer.

NIH DSLD market slice

Median50 mcg
Products27,296
Below90%

Bulk CSV dump 16 January 2026 · label entries through 2025. Disclosed amounts only — proprietary blends without gram weights excluded.

Trial floors

Primary

Oral repletion (deficiency confirmed) · 1,000 mcg over 1 year (medium evidence) · Benefit shown — 1000 mcg/day oral methylcobalamin for a year normalised B12 and improved nerve conduction in metformin-treated diabetic neuropathy; the Cochrane review found oral matches intramuscular for correcting levels. After labs, with clinician oversight.

Secondary

Typical multivitamin (not therapeutic) · 6–25 mcg (high evidence) — Illustrative floor only — not sufficient for metformin-associated deficiency repletion.

Label reading notes

  • Serum B12 (± MMA) before high-dose repletion — labels cannot diagnose deficiency. A daily multivitamin (often 6–25 mcg) is not therapeutic repletion after confirmed deficiency.
  • Repletion trials in metformin users used 1000 mcg/day oral cyanocobalamin or methylcobalamin. Cochrane data support high-dose oral against intramuscular for correcting levels; sublingual upsells are usually marketing at that dose.
  • Check serving size on gummies and sprays — some split 1000 mcg across two pieces or list compound weight instead of micrograms of B12.
  • After repletion, maintenance dose and duration are clinician decisions, especially with neuropathy, prior GI surgery, or persistent symptoms despite normal labs.