Conclusion: Subgroup analyses indicated that the use of vitamin B12 supplements among vegans contributes to significant improvements in all biomarker concentrations compared to their unsupplemented counterparts. Our findings underscore the need for improved strategies to redress poor vitamin B12 status with appropriate B12 supplementation use among those adhering to vegetarian and vegan diets.
PubMed 39373282 ↗Vitamin B12
People mainly take Vitamin B12 for energy, mood, focus. Based on 277 first-hand reports and 376 meta-analyses & systematic reviews in the medical literature. Ranked #127 of 1,974 overall.
Of reports that state an outcome, 70% are positive.
What Vitamin B12 does, according to users
Of the people who reported each effect, the share who said it got better.
1 more with fewer than 3 reports
What the research says
Systematic reviews and meta-analyses from PubMed, with their published conclusions.
3+ meta-analyses or systematic reviews and 10+ randomized controlled trials in humans. The grade measures how much human research exists — read the conclusions below for what it found.
Conclusion: The evidence suggests an association between elevated B12 with a higher risk of cancer, with risk ratios ranging 1,88 to 5,9. There was less consistent evidence linking vitamin B12 and mortality.
PubMed 38953509 ↗Conclusion: In conclusion, maintaining optimum serum levels of nutrients and vitamins, either through a balanced and healthy diet consuming fresh fruits, vegetables, and fats or by taking appropriate supplementation, is essential in maintaining optimal health-related quality of life and reducing the risk for women during the menopausal transition and after menopause. Nevertheless, more recent studies need to be assessed to formulate adequate recommendations to achieve positive clinical outcomes.
PubMed 38935105 ↗Conclusion: All IM, oral, and SL routes of administration of vitamin B12 can effectively increase the level of vitamin B12 without significant differences between them, as thought previously. However, the IM route was the top-ranked statistically but without clinical significance. We found no significant difference among studied administrated routes in all other CBC parameters and homocysteine levels.
PubMed 38231320 ↗Dosage people report
As stated by users — not a recommendation. Follow the label or your doctor.
Reported side effects
How often each side effect came up across all reports.
What users say
Verbatim quotes, shortened only — each links to the original discussion.
“the pharmacist gave me a 1ml B12 shot for $15 and then ordered me a vial of 30ml so I could do it at home”
“And you can just take B12 alongside it. It does deplete it.”
“sometimes b12”
“B-12 500mcg”
“Vitamin B12”
Top discussions (5)
- Three weeks ago I asked why some people still wake up foggy after 8 hours of sleep. I went through 300+ replies. Here’s what kept coming up. ↗
- There is a life before supplementing B12 and there's one after ↗
- Started supplements in my 30s after a lifetime of unexplained fatigue and anxiety — I thought it was just my personality. It wasn't. ↗
- Sema —> Tirz (-30lbs down) ↗
- What are your top 3-5 Peptides OTHER than GLPs? ↗
Other options for energy
User data from public discussions; research from PubMed. Information only, not medical advice — talk to a doctor before starting, stopping or combining anything. Data updated October 2, 2026. How we rate