People mainly take Vitamin B for energy, focus, skin & hair. Based on 22 first-hand reports and 638 meta-analyses & systematic reviews in the medical literature. Ranked #809 of 1,974 overall.
Of reports that state an outcome, 42% are positive.
Of the people who reported each effect, the share who said it got better.
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: Further, only one study reported effects on idiopathic fatigue, and therefore, no analysis was possible. Vitamin B12 supplementation is likely ineffective for improving cognitive function and depressive symptoms in patients without advanced neurological disorders.
PubMed 33809274 ↗Conclusion: Raw milk consumption was not associated with cancer (two studies) or lactose intolerance (one study). Overall, these findings should be interpreted with caution given the poor quality of reported methodology in many of the included studies.
PubMed 22054181 ↗Conclusion: This meta-analysis suggests that B vitamin supplementation is associated with slowing of cognitive decline, especially in populations who received early intervention and intervention of long duration; the study also indicates that higher intake of dietary folate, but not B12 or B6, is associated with a reduced risk of incident dementia in non-dementia aged population. Given the prevalence of dementia cases in many countries with aging populations, public health policies should be introduced to ensure that subgroups of the population at risk have an adequate B vitamin status.
PubMed 34432056 ↗Conclusion: PN is associated with lowered plasma vitamin B12 and elevated methylmalonic acid and homocysteine. Overall, interventional studies have suggested that B-vitamins could improve symptoms of PN. Available trials have limitations and generally did not investigate vitamin status prior to treatment. Well-designed studies, especially in non-diabetes PN, are needed. This meta-analysis is registered at PROSPERO (ID: CRD42020144917).
PubMed 33619867 ↗As stated by users — not a recommendation. Follow the label or your doctor.
How often each side effect came up across all reports.
Verbatim quotes, shortened only — each links to the original discussion.
“Vit B, D, other things”
“You just gotta take a B supplement with metformin. Metformin use lowers your B vitamins.”
“I supplement the basics like vit d, magnesium glycinate, iron, copper, vit bs, etc.”
“I take a stack with fish oil, vitamin D, and vitamin B in it.”
“Some evidence for B vitamins too (if deficient).”
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