Vitamin B6 for PMS: What the Trials Show, and Why a Bigger Dose Is Not Better
Vitamin B6 is one of the oldest supplement suggestions for premenstrual syndrome. The trials lean positive for mood symptoms, but most are small and old, benefit did not rise with dose, and high doses can damage nerves. Here is what the studies found and who should be careful.
By Kymata Health Editorial Published Last checked
Key takeaways
From 6 sources- A 1999 BMJ review of 9 trials (940 women) found women were more likely to report overall improvement on B6 than on placebo (odds ratio 2.32), but most trials were low quality1.
- Benefit did not rise with dose, and the review authors saw no rationale for more than 100 mg a day1.
- In a 63-woman crossover trial, 50 mg a day helped emotional symptoms such as depression, irritability and tiredness, but no other symptom type2.
- In a 120-woman trial of severe PMS, symptoms fell 45.3% on 300 mg a day of B6, close to the 39.4% to 46.1% seen on placebo, while fluoxetine 10 mg cut them 65.4%4.
- The US adult upper limit for B6 is 100 mg a day, and long-term high doses can cause sensory nerve damage5.
What this article covers
1 evidence profileThe evidence, graded
Pulled from the trial tables in our evidence profiles. Grades follow our evidence-grading policy.
Graded findings
1 row- CGrade CPremenstrual symptomsImproved Women were more likely to report overall improvement with B6 than placebo (OR 2.32); depressive symptoms also improved (OR 1.69; 4 trials, 541 women). The authors note most trials were low quality.Vitamin B6 (pyridoxine vs P5P) · Systematic review · n=940 · 1999 · PMID 10334745
What the pooled trials found
The best summary of vitamin B6 for premenstrual syndrome is still a 1999 systematic review in the BMJ, which pooled 9 placebo-controlled trials with 940 women1.
Women taking B6 were more likely to say their overall symptoms improved (odds ratio 2.32, 95% CI 1.95 to 2.54), and premenstrual depression improved too (odds ratio 1.69 across 4 trials and 541 women)1. That headline figure leaves out one trial with an unusually large placebo response; with it included, the odds ratio fell to 1.571.
The authors were blunt about the limits. Only one trial was large enough for adequate statistical power, three of the nine tested Optivite, a multivitamin supplying 600 mg of B6 a day, and two looked only at breast pain1. They concluded that 100 mg a day, and possibly 50 mg, is likely to help, but that a properly powered trial was still needed1.
The review itself had no funding. One author reported lecture fees and research funding from several drug companies, including Eli Lilly, SmithKline Beecham and Zeneca1.
What individual trials add
- General-practice crossover trial, 1989: 63 women aged 18 to 49 took 50 mg of B6 a day or placebo for 3 months each, and 32 finished all 7 months2. B6 helped emotional symptoms (depression, irritability and tiredness) but no other symptom type2.
- Double-blind trial, 2007: in 94 women, 80 mg a day over three cycles was linked to lower scores for moodiness, irritability, forgetfulness, bloating and especially anxiety, as summarized by the NIH Office of Dietary Supplements5.
- Magnesium plus B6, 2000: 44 women took 200 mg of magnesium, 50 mg of B6, both, or placebo, each for one cycle3. Only the combination reduced anxiety-type symptoms such as nervous tension and mood swings, and the authors called the effect modest3.
- Severe PMS, 1998: 120 women in four groups each took 3 months of placebo and 3 months of a drug4. Symptoms fell 45.3% on 300 mg a day of B6, about the same as the 39.4% to 46.1% drop on placebo; fluoxetine 10 mg cut them 65.4%4.
Dose: why more is not better
Across the pooled trials there was no link between dose and benefit, and the review authors saw no rationale for daily doses above 100 mg1. Only 1 of the 940 women reported a side effect that could fit B6 nerve toxicity, but the trials were short and participants were not assessed by a neurologist1.
The US Food and Nutrition Board set the adult upper limit at 100 mg a day, and chronic intakes of 1 to 6 g a day for 12 to 40 months have caused severe, progressive sensory neuropathy5. In 2023, the European Food Safety Authority set a much lower adult upper limit of 12 mg a day5. Our B6 safety explainer covers the symptoms and label math.
B6 is sold alone and inside multivitamins and B-complex products, so the total from every label counts5. The vitamin B6 page lists the forms and studied doses.
How B6 compares with other PMS options
For severe symptoms, prescription options have stronger trial evidence. In the four-drug trial above, fluoxetine reduced symptoms more than B6, alprazolam or propranolol4. Severe mood symptoms before a period can signal premenstrual dysphoric disorder, which is worth raising with a clinician.
Among supplements, vitex has a few well-run PMS trials of branded extracts, covered in our vitex review. Magnesium plus B6 had a small effect on anxiety-type symptoms in one short trial3; see magnesium for anxiety for that evidence.
Who should be careful
B6 interacts with several medicines and can harm nerves at high doses. Check with a prescriber or pharmacist first if any of these apply:
- Antiepileptic drugs: valproic acid, carbamazepine and phenytoin speed B6 breakdown, and pyridoxine at 200 mg a day for 12 to 120 days can lower blood levels of phenytoin and phenobarbital5.
- Levodopa taken without carbidopa: the carbidopa-levodopa label says oral pyridoxine at 10 to 25 mg may undo the effect of levodopa alone; carbidopa blocks this interaction6.
- Cycloserine or theophylline: cycloserine increases urinary loss of B6, and people taking theophylline often have low B6 levels, so the prescriber should know about any supplement5.
- Pregnancy: the NIH Office of Dietary Supplements advises talking to a physician before using B6 for morning sickness, because doses could approach the upper limit5.
- Tingling, numbness or unsteadiness on B6: stop and get checked, since symptoms usually ease when B6 is stopped early5.
- Several supplements at once: add up B6 from every product against the 100 mg adult upper limit5.
Quick answers
Common questions
4 answersHow much vitamin B6 was used for PMS in trials?
How long does vitamin B6 take to work for PMS?
Is B6 or magnesium better for PMS?
Neither has strong trials on its own. In one 44-woman trial, only the combination of 200 mg magnesium and 50 mg B6 eased anxiety-type symptoms3.
Keep reading
Full evidence profiles
Every graded study, studied doses, interactions and safetyRelated articles
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References
6 sources. Numbers in the text link here.
Sources cited in this article
6 sources- 1Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic reviewBMJ, 1999 · PMID 10334745
- 2Pyridoxine (vitamin B6) and the premenstrual syndrome: a randomized crossover trialJ R Coll Gen Pract, 1989 · PMID 2558186
- 3A synergistic effect of a daily supplement for 1 month of 200 mg magnesium plus 50 mg vitamin B6 for the relief of anxiety-related premenstrual symptoms: a randomized, double-blind, crossover studyJ Womens Health Gend Based Med, 2000 · PMID 10746516
- 4A double-blind trial of four medications to treat severe premenstrual syndromeInt J Gynaecol Obstet, 1998 · PMID 9722128
- 5Vitamin B6: Fact Sheet for Health ProfessionalsNIH Office of Dietary Supplements, 2023
- 6SINEMET (carbidopa and levodopa) tablets: prescribing informationOrganon LLC, via DailyMed (label effective August 2026), 2026
Vitamin B6 (pyridoxine vs P5P) and other dietary supplements are not intended to diagnose, treat, cure or prevent any disease, and these statements have not been evaluated by the FDA. Talk to your clinician or pharmacist before starting a supplement, especially if you take prescription medicines. This page has no product or affiliate links.