Vitamin B12 is one of the few supplements where the question “do I actually need this?” has a clear answer for some groups — and a clear “probably not” for everyone else.
Who genuinely needs it
B12 occurs naturally almost only in animal foods. That makes supplementation a real requirement for vegans, and worth attention for vegetarians. Two other groups matter: adults over about 50, whose ability to release B12 from food declines, and people taking metformin or long-term acid-reducing medication, both of which can reduce absorption. The NIH Office of Dietary Supplements covers this in its consumer sheet on vitamin B12.
Why deficiency is easy to miss
Symptoms — fatigue, weakness, pins and needles, brain fog, low mood — are vague and easy to attribute to a busy life. B12 deficiency can also cause nerve damage that does not fully reverse, which is why it is worth a blood test rather than guesswork if you are in one of the at-risk groups.
Forms and amounts
The RDA for adults is 2.4 mcg, but supplements routinely contain far more because absorption from a single large dose is inefficient. Cyanocobalamin is the cheapest and best-studied form; methylcobalamin is popular and also works. Sublingual tablets are not clearly superior to swallowed ones for most people — both work.
Vitamin B12 (e.g. Nature Made, NOW)
- Cyanocobalamin is cheap and well studied; methylcobalamin also works
- Doses far above the 2.4 mcg RDA are normal — absorption is inefficient
- A blood test beats guessing if you are in an at-risk group
Very inexpensive
Check Price →Safety notes
B12 is water-soluble with no established upper limit — excess is generally excreted, which is why high-dose products are common and not alarming. That said, if you have symptoms suggesting deficiency, see a healthcare provider rather than self-treating: some causes (such as pernicious anemia) need injections, not tablets.
See also our guide to whether multivitamins are worth it.