Nutrition
How much B12 should vegans take?
Short answer
Common patterns: 25–100 µg cyanocobalamin daily, or 1000 µg two to three times a week. Check the label and a clinician, especially if you already have a deficiency.
B12 is not reliably present in unfortified plant foods. Ferments and spirulina do not replace a supplement. Deficiency shows up after months or years because the liver stores it.
Cyanocobalamin is cheap, stable and the best studied. Methylcobalamin works for many people, but dosing is less standardised. Absorption falls after 50 — blood tests help.