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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Trial reference

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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.

Want the outcome before the arithmetic? The reason check opens any registry entry on this page with its trial result first, then compares your daily intake with the studied amount.

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 · how we grade this) · 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 · how we grade this) — 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.