Evidence explainerVitamin B6 (pyridoxine vs P5P)

Vitamin B6 Toxicity: How a “Harmless” Vitamin Can Cause Tingling Feet

B6 hides in energy drinks, B-complexes, magnesium blends and sleep formulas. High intakes over months can damage nerves. Here is the limit and what the research says about forms.

By Kymata Health editorial teamPublished October 9, 2026Last reviewed October 9, 2026

Medical review pending. Written by our editorial team from the studies cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • Long-term intakes of 1 to 6 g/day for 12 to 40 months can cause severe, progressive sensory neuropathy, and some reports describe it below 500 mg/day [1].
  • The adult upper limit is 100 mg/day, set at half the 200 mg/day level studied for up to 5 years without neuropathy [1].
  • The adult RDA is only 1.3 mg/day (1.5 to 1.7 mg after 50) [1].
  • Symptoms usually stop if B6 is stopped when they first appear [1].
  • NIH reports absorption does not differ substantially between pyridoxine and P5P [1].

The evidence, graded

Pulled from our monograph evidence tables. Grades follow our evidence-grading policy.

  • No effectNo effectThinking skills in healthy adults in mid and late life (B vitamins)Vitamin B6 (pyridoxine vs P5P) · Systematic review · n=27,882 · 2018 · PMID 30556597B vitamin supplements probably have little or no effect on overall cognitive function up to 5 years (SMD -0.03 to 0.06), and may have none at 5-10 years.
  • Grade CImprovedPremenstrual symptomsVitamin B6 (pyridoxine vs P5P) · Systematic review · n=940 · 1999 · PMID 10334745Women 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.

How much is a lot

Adults need 1.3 mg a day up to age 50, and 1.7 mg (men) or 1.5 mg (women) after [1]. The upper limit is 100 mg/day from food and supplements [1]. The Food and Nutrition Board set it by halving the 200 mg/day level that had been studied for up to 5 years without nerve problems, because long-term harm data are limited [1].

What too much does

NIH describes severe, progressive sensory neuropathy with chronic intakes of 1 to 6 g/day for 12 to 40 months, and notes some reports below 500 mg/day [1]. Excessive intakes have also caused skin lesions, light sensitivity, nausea and heartburn [1]. The usual good news: symptoms generally stop if B6 is stopped when they first appear [1].

Because B6 shows up in so many combination products, it is worth adding up the B6 line on every label you take, because the adult upper limit of 100 mg a day covers your total intake [1].

Is P5P safer or better?

Most supplements contain pyridoxine hydrochloride; some contain pyridoxal 5’-phosphate (PLP or P5P), the active coenzyme [1]. NIH reports absorption does not differ substantially among forms, and we found no head-to-head outcome trials comparing them [1].

What higher-dose B6 has been studied for

A 1999 review of 9 trials (940 women) found more women with premenstrual symptoms reported improvement on B6 at up to 100 mg/day, but most trials were low quality [2]. In a Cochrane review of 14 trials in mid- and later-life adults, B vitamins including B6 probably had little or no effect on cognitive function up to 5 years [3].

B6 also interacts with some medicines: antiepileptic drugs speed its breakdown, and 200 mg/day can lower phenytoin and phenobarbital levels [1]. If you take those, talk to your clinician. Related reads: folic acid and B12 after 50 and methylcobalamin vs cyanocobalamin. Full details on the vitamin B6 monograph.

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References

  1. [1]Vitamin B6: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements, 2023.
  2. [2]Efficacy of vitamin B-6 in the treatment of premenstrual syndrome: systematic review. BMJ, 1999. PMID 10334745
  3. [3]Vitamin and mineral supplementation for maintaining cognitive function in cognitively healthy people in mid and late life. Cochrane Database Syst Rev, 2018. PMID 30556597

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.

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