Vitamin B12 (Methylcobalamin)
B12 is virtually absent in plant foods — non-negotiable for vegans.
- Typical dose
- 500 mcg
- When to take
- Morning
- Onset
- Weeks to months to correct deficiency; energy and cognitive benefits can be noticed earlier in deficient individuals
What it does
Benefits
- Essential for red blood cell formation — prevents anemia
- Required for myelin sheath — nerve function and cognition
- Supports methylation (DNA synthesis, homocysteine metabolism)
- Deficiency causes irreversible nerve damage if prolonged
The science
How it works
B12 (cobalamin) is a cofactor for methionine synthase and methylmalonyl-CoA mutase. Only produced by bacteria — found almost exclusively in animal foods or fortified products.
Getting it right
Dose & timing
Dose guidance
500–1000 mcg/day methylcobalamin or cyanocobalamin for vegans and vegetarians. Deficient individuals may need higher doses or injections under medical guidance.
Best time to take
Morning. Sublingual absorbs without needing intrinsic factor.
Is it for you?
Who should (and shouldn't) take it
Good for
- Vegans — non-negotiable
- Vegetarians — recommended
- Adults over 50 (reduced absorption from food)
- People on metformin or PPIs (both reduce B12 absorption)
Skip or ask a doctor if
- Leber's disease (rare eye condition)
- You should confirm deficiency with bloodwork before injections
Know before you start
Side effects & safety
- Essentially none — excess is excreted
- Rare: acne flare, anxiety at very high doses
Shopping guide
Forms & what to look for
- Methylcobalamin
Active form; preferred by some
- Cyanocobalamin
Cheapest, stable, well-researched
- Hydroxocobalamin
Used in injections
- Sublingual
Absorbs without intrinsic factor
Combining
Stacks well with / avoid pairing
Stacks well with
Common questions
FAQ
Methyl vs cyano form?
Cyano is cheap and converts fine for most. Methyl is the active form and preferred for those with MTHFR variants or neurological issues.
Can I get B12 from nutritional yeast?
Only if fortified — read the label. Natural plant foods don't reliably contain active B12.
Do I really need 1000 mcg when RDA is 2.4?
Yes — absorption is very inefficient at high oral doses (only ~1% absorbed). Supplement doses intentionally oversupply.
References
Sources & further reading
Educational only, not medical advice. Check with a clinician before starting anything new, especially if you're on medication or pregnant.
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