What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
Vitamin B12 benefits: where the science stands
For energy and fatigue: not settled yet.
Energy and fatigue are what most people take vitamin B12 for, and the strongest evidence says it does not help: a combined review found no real difference. As of August 2026, the verdicts on this page rest on evidence from 39 trials, drawn from the strongest research among the 4,086 papers on PubMed that mention vitamin B12. Every claim is checked below.
4,086 papers on PubMed · evidence from 39 trials · 1 caution
Claim by claim
- Energy and fatigueThe science is still forming. No real difference found so far.
- Anaemia and iron levelsThe science is still forming. No real difference found so far.
- HeartWell studied, and it does not work. The biggest review covered 15 trials.
- Memory and focusWell studied, and it does not work. The biggest review covered 16 trials.
See 5 more scored claims+
- MoodWell studied, and it does not work. The biggest review covered 16 trials.
- Nerve painThe science is still forming. The best studies disagree.
- PregnancyThe science is still forming. No real difference found so far.
- SleepThe science is still forming. No real difference found so far.
- Stress and anxietyThe science is still forming. No real difference found so far.
Pairs people ask about
The nine sources we read
- 2017Meta-analysis · pools 15 trials, 71,422 people · no clear effect on heartsource
- 2017Meta-analysis · no clear effect on stress and anxietysource
- 2021Randomized trial · 90 people · benefit for nerve painsource
- 2021Meta-analysis · no clear effect on energy and fatigue; no clear effect on memory and focus; no clear effect on moodsource
- 2022Randomized trial · 265 people · no clear effect on stress and anxietysource
- 2022Observational study · no clear effect on memory and focussource
- 2022Randomized trial · 600 people · no clear effect on sleepsource
- 2023Meta-analysis · no clear effect on nerve painsource
- 2024Meta-analysis · pools 2 trials, 284 people · no clear effect on anaemia and iron levels; no clear effect on pregnancysource
Chosen as the strongest evidence out of 4,086 papers on PubMed. Every row links to its paper.
Fair questions
Does vitamin B12 work?+
For energy and fatigue, it is not settled. No real difference found so far.
Is vitamin B12 safe?+
One caution is recorded: Searching 21 health outcomes returned no trial of vitamin B12 on its own for any of them. This is not the same as a supplement nobody has studied. Vitamin B12 is a nutrient your body needs, and there is research on it. What that research is about is correcting a measured deficiency, and multi-vitamin formulations where B12 is one ingredient among many. None of it tells you whether taking extra helps someone who already gets enough.
Why only 9 sources, when PubMed lists 4,086?+
The 4,086 is every paper that mentions vitamin B12 in any way: animal studies, blood measurements, papers where it is a side note. The strongest sources are combined reviews, and each one already gathers every trial its authors could find. Our 9 cover 39 trials between them, and every one is linked above. Both counts are measured, not estimated.