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1Essential

Vitamin B12

Also sold as Cobalamin, methylcobalamin, cyanocobalamin

Found almost only in animal foods. Lifelong for vegans and commonly needed over 60.

1TrustedSupp Tier System™ · Tier 1Take persistently

How long to take it

Ongoing for vegans, over-60s, and anyone on metformin or long-term acid blockers. Nerve damage from prolonged deficiency can become permanent.

Who it's actually for

Plant-based eaters, older adults, people on metformin or PPIs, and anyone post-bariatric surgery.

Safe upper limit

Reported
None established
Water-soluble and remarkably non-toxic; excess is excreted. The risk is under-treating, not over-treating.
Vitamin B12 — Health Professional Fact SheetNot re-checked
Widely reported as having no UL due to low observed toxicity — not re-checked against the live fact sheet this session.

Interactions to know about

  • Metformin specifically — Also included in diabetes medication
  • Acid blockers — Omeprazole, lansoprazole, famotidine

Other supplements:

Run your full list through the interaction check.

Practical notes

  • Ask for B12 and, if borderline, methylmalonic acid — it catches deficiency earlier.
  • Folate supplements can mask B12 deficiency while nerve damage continues.
  • Sublingual and oral work for most people; injections are for absorption failure.