Dosage · Supplement
Vitamin B12: dosage and how to take it
50–250 µg/day, or 1,000 µg 2–3×/week.
- Overall grade
- Grade A
- Last revised
- 0
- graded outcomes
- 0
- references listed
Assembled by the app from other entries in this library. It adds no evidence of its own — follow the links to the entries it draws on.
The evidence in words
How much to take
For maintenance in vegans, 50–250 µg/day oral (or 1,000 µg a few times weekly) works because passive absorption covers a fraction of large doses. Confirmed deficiency with neurological signs is a medical matter and often treated with injections. Methylcobalamin and cyanocobalamin are both effective.
Timing & separation
There are no strict timing conflicts on record for Vitamin B12; consistency matters more than the exact hour for most goals.
Why the dose is what it is
B12 is a cofactor for two enzymes: methionine synthase (regenerating methionine and folate, tying it to homocysteine and methylation) and methylmalonyl-CoA mutase. Absorption is a multi-step process requiring stomach acid and intrinsic factor — which is why acid-suppressing drugs and gastric/ileal disease impair it.
Bottom line
If you eat little or no animal food, or take metformin or a PPI long-term, supplement B12 or test — the downside of deficiency (permanent nerve damage) is far worse than the trivial cost of prevention.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Vegan maintenance
- 50–250 µg/day, or 1,000 µg 2–3×/week.
- Deficiency
- Medical management; often injections initially.
Goes with
- Vitamin B12Full Vitamin B12 monographEvidence grade A
Related reading
Entries that share this one's tags or conditions.
- Vitamin B12 for Cognitive declineEvidence grade C — Corrects deficiency-linked decline onlyEvidence grade C
- Vitamin B12 for Correcting deficiency / anemiaEvidence grade A — DefinitionalEvidence grade A
- Vitamin B12 for Energy in replete peopleEvidence grade D — No effect without deficiencyEvidence grade D
- Vitamin B12 for Neuropathy (early deficiency)Evidence grade A — Reversible if caught earlyEvidence grade A
Sources
This entry lists no references of its own — it is assembled from the entries it links to, whose sources are on their pages.
Last revised . A grade is this entry's reading of the evidence, not medical advice.