Supplement analysis backed by scientific evidence · PT · ES · DE · FR

← All supplements
Moderate evidenceVitamins & minerals

Vitamin B6 (Pyridoxine)

Vitamin B6 has genuine, specific uses — nausea in pregnancy, isoniazid-induced neuropathy, and possibly PMS — but it is also the one water-soluble vitamin with well-documented nerve toxicity at doses people routinely buy over the counter.

View on iHerb Ships to 180+ countries · welcome discount for new customers

What the science says

  • Reduces nausea and vomiting of pregnancy Strong evidence

    Pyridoxine 10-25 mg every 6-8 hours, alone or combined with doxylamine, is first-line therapy for nausea and vomiting of pregnancy in ACOG and Canadian obstetric guidance, based on randomised trials showing reduced nausea scores versus placebo. The doxylamine-pyridoxine combination is an approved prescription product in several countries.

  • Improves premenstrual syndrome symptoms Moderate evidence

    A systematic review of nine placebo-controlled trials (940 women) found B6 up to 100 mg/day roughly doubled the odds of overall PMS symptom improvement (OR ~2.3) and of depressive symptom improvement (OR ~1.7). The authors flagged low methodological quality across the included trials, so treat the effect size as soft.

  • Prevents isoniazid-induced peripheral neuropathy Strong evidence

    Isoniazid depletes pyridoxal phosphate, and co-administration of pyridoxine 25-50 mg/day is standard tuberculosis practice to prevent the resulting neuropathy. This is an established pharmacological indication rather than a nutritional one.

  • Is harmless at high doses Limited evidence

    Chronic intake above roughly 50 mg/day — and clearly above 200 mg/day — can cause a dose- and duration-dependent sensory peripheral neuropathy with numbness, ataxia and burning pain. Cases have been reported at doses well within the range sold on shelves, and recovery after stopping is usually but not always complete. Several regulators have moved to cap over-the-counter B6 content for this reason.

Dosage & safety

Studied doseRDA is 1.3 mg/day for adults under 50, rising to 1.7 mg (men) and 1.5 mg (women) after 50. Nausea of pregnancy: 10-25 mg every 6-8 hours. PMS trials used 50-100 mg/day. Isoniazid prophylaxis: 25-50 mg/day. Tolerable upper limit for adults is 100 mg/day, and there is little reason to exceed 50 mg/day for long periods. Pyridoxal-5'-phosphate (P5P) is often marketed as safer, but elimination of neuropathy risk with chronic high dosing has not been demonstrated.
SafetyDose-dependent sensory peripheral neuropathy is the defining risk — numbness, tingling, gait unsteadiness — reported with chronic use above ~50 mg/day and well documented above 200 mg/day. Discontinue immediately and seek medical review if these appear. B6 reduces levodopa efficacy when levodopa is given without carbidopa, and may lower phenytoin and phenobarbital levels. Observational data link long-term high-dose B6 (with B12) to increased hip fracture risk and, in male smokers, to lung cancer. Pregnancy doses in the 10-75 mg/day range are considered safe and are guideline-endorsed. Check multivitamins and 'energy' or 'nerve support' products — stacked B6 doses add up quickly.

How to take it

TimingTiming does not matter; for pregnancy nausea it is dosed every 6-8 hours.
With food?With food.
Worth knowingNew numbness or tingling in the hands or feet means stop and get reviewed — B6 neuropathy is the one clear harm and it is dose- and duration-dependent.

Interactions

With medications

  • levodopa given without carbidopa

    B6 accelerates peripheral breakdown of levodopa and markedly reduces its effect. avoid supplemental B6 unless your levodopa is combined with carbidopa — check with your neurologist

  • phenytoin and phenobarbital

    High-dose B6 can lower blood levels of these antiepileptics and reduce seizure control. do not take high-dose B6 without telling your neurologist

  • isoniazid

    Isoniazid depletes B6 and causes peripheral neuropathy; B6 is deliberately co-prescribed to prevent it. take the 25-50 mg/day your doctor prescribes alongside it

With other supplements

  • multivitamins, 'energy' and 'nerve support' blends

    B6 doses stack across products and the neuropathy risk depends on your total, not any one label. add up B6 across everything you take and keep the total well under 50 mg/day long-term

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does vitamin B6 work for morning sickness?

Yes — the evidence is strong. Vitamin B6 (pyridoxine) at 10–25 mg every 6–8 hours, alone or with doxylamine, is first-line therapy for nausea and vomiting of pregnancy, based on randomised trials.

Can too much vitamin B6 cause nerve damage?

Yes. Chronic vitamin B6 intake above about 50 mg/day, and clearly above 200 mg/day, can cause numbness, tingling and unsteadiness. If these appear, stop vitamin B6 and get medically reviewed.

Does vitamin B6 help PMS symptoms?

Possibly — the evidence is moderate but soft. A review of nine trials found vitamin B6 up to 100 mg/day roughly doubled the odds of overall symptom improvement, but the trials were of low quality.

How much vitamin B6 per day is safe?

The adult upper limit for vitamin B6 is 100 mg/day, and there is little reason to exceed 50 mg/day for long periods. Add up vitamin B6 across multivitamins and energy or nerve blends, since the risk depends on your total.

Scientific references

Where to buy

Swanson Vitamins, Vitamin B6 Pyridoxine, 100 mg, 250 Vegan Capsules

View on iHerb

Ships to 180+ countries · welcome discount for new customers

Referral link — this site may earn a commission on purchases.

Related in Vitamins & minerals