Vitamin B12
An essential B vitamin for nerves, red blood cells, and energy metabolism.
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What it is
Vitamin B12 is needed to make red blood cells, maintain nerves, and metabolize energy. It's found almost exclusively in animal foods, so plant-based eaters are a key at-risk group.
How it works
Vitamin B12 is essential for making red blood cells, maintaining the protective sheath around nerves, and DNA synthesis. It needs stomach acid and a protein called intrinsic factor to be absorbed, which is why absorption problems — not just low intake — are a common cause of deficiency.
What it's been studied for
Used to correct or prevent B12 deficiency and support energy and nerve health.
What the evidence shows
B12 is genuinely essential, and correcting a deficiency resolves real symptoms like fatigue and nerve problems. But if you're not deficient, extra B12 doesn't add energy. At-risk groups include vegans, older adults, and people on metformin or long-term acid reducers.
Who should consider it
The key at-risk groups are vegans and vegetarians (B12 is almost only in animal foods), older adults (who absorb it less efficiently), and people on metformin or long-term acid reducers. Deficiency can cause fatigue, tingling, balance problems, and cognitive changes.
Amounts commonly studied
Correcting low levels often uses higher oral doses (500-1,000 mcg); maintenance needs are much smaller. Testing guides the need.
How to take it
For correcting low levels, higher oral doses (500-1,000 mcg) are common; ongoing maintenance needs are far smaller. Sublingual and injectable forms are used when absorption is impaired. It's water-soluble, so timing is flexible and excess is excreted.
Forms & absorption
Methylcobalamin and cyanocobalamin are both effective; sublingual and injectable forms are used when absorption is impaired.
Food sources
Meat, fish, shellfish, eggs, and dairy are the natural sources; fortified cereals, plant milks, and nutritional yeast are the practical options for plant-based eaters.
Safety & interactions
Very safe and water-soluble, with excess excreted. Persistent fatigue or nerve symptoms deserve testing rather than guesswork.
Myths & what it won't do
Myth: B12 shots or high doses energize everyone. Reality: they only help if you're actually deficient. Myth: eating meat guarantees you're fine. Reality: absorption declines with age and certain medications, so even meat-eaters can run low — testing settles it.
Common questions
- Which form is best?
- Methylcobalamin and cyanocobalamin are both effective; sublingual or injectable forms are used when absorption is a problem.
- Do vegans need to supplement B12?
- Yes — reliable B12 comes almost entirely from animal foods or fortification, so a supplement is strongly recommended on a vegan diet.
- Can you take too much?
- It's water-soluble with low toxicity, so excess is generally excreted; still, high doses are only needed to correct a confirmed shortfall.
The amounts listed here are what published research has used — not a prescription or a recommended dose for you. Confirm anything you plan to take with your own healthcare provider, especially if you take medications, are pregnant or nursing, or have a health condition.
Related goals
Research on Vitamin B12
Recommendations on this page are informed by published research. This is educational information, not medical advice.
- Stabler SP. Clinical practice. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-160. View study →Note: Clinical review of B12 deficiency, including at-risk groups (older adults, vegans, metformin and acid-reducer users) and treatment.