NutriDex

The Supplement Research Compendium
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Vitamin B6 (Pyridoxine)

Pyridoxine / P5P

The amino-acid and neurotransmitter coenzyme — essential, but a poor supplement for the well-nourished

Strong evidence 🍊Vitamin

✚ Updated · How we grade evidence

Evidence tier
Strong
Research weight
Citations
11 verified / 11
Classification
Vitamin
❝
What the evidence says. Multiple high-quality RCTs / meta-analyses with consistent effects.

What is Vitamin B6 (Pyridoxine)?

Vitamin B6 (Pyridoxine) (Pyridoxine / P5P) is a vitamin used for corrects deficiency: reverses b6-deficiency anemia, dermatitis, glossitis, neuropathy, and seizures (including isoniazid- or hydralazine-induced and rare pyridoxine-dependent infantile seizures). NutriDex grades the human evidence as Strong. Vitamin B6, as the active coenzyme pyridoxal-5'-phosphate (PLP), drives over 100 enzymatic reactions, chiefly in amino-acid metabolism, neurotransmitter synthesis (serotonin, GABA, dopamine), heme synthesis, and homocysteine catabolism. Frank deficiency is rare in isolation but causes microcytic anemia, dermatitis, glossitis, peripheral neuropathy, depression, and seizures (classically in isoniazid use, alcoholism, or renal dialysis). In non-deficient people, supplementation has largely failed to deliver clinical benefit: despite lowering homocysteine by roughly 25-30% as part of B6/B9/B12 regimens, large RCTs (HOPE-2, VITATOPS) and a 2017 Cochrane review found no reduction in cardiovascular events or mortality, and a prospective cohort linked high-dose individual B6 supplements (>20 mg/d) to increased lung cancer risk in men, especially smokers. Its best-validated supplemental role is pyridoxine (alone or with doxylamine) as first-line therapy for nausea and vomiting of pregnancy.

Purported Benefits

✓Corrects deficiency: reverses B6-deficiency anemia, dermatitis, glossitis, neuropathy, and seizures (including isoniazid- or hydralazine-induced and rare pyridoxine-dependent infantile seizures)
✓First-line for nausea/vomiting of pregnancy: pyridoxine 10-25 mg, alone or combined with doxylamine, is recommended by ACOG as safe and effective initial therapy
✓Lowers plasma homocysteine ~25-30% as part of folic acid + B12 + B6 regimens (a biomarker effect that did NOT translate into fewer cardiovascular events in trials)
✓Prevents isoniazid-induced neuropathy when co-prescribed prophylactically during tuberculosis treatment
✓Modest, low-certainty symptom relief in premenstrual syndrome and possibly carpal tunnel symptoms — evidence is weak and not a substitute for definitive therapy
✓Does NOT prevent cardiovascular events, stroke disability, cancer, or cognitive decline in replete people; high individual-supplement doses may carry a lung-cancer signal in male smokers

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Corrects B6 deficiency (anemia, neuropathy, seizures)Established treatment reversing deficiency syndromes including isoniazid- and pyridoxine-dependent seizures. Strong ↑ benefit · large 1
Treats nausea/vomiting of pregnancyACOG first-line; effective but a reanalysis found the doxylamine combo missed the prespecified clinical threshold. Strong ↑ benefit · moderate 2
Lowers plasma homocysteineReliably cuts homocysteine ~25-30% in B-vitamin regimens, but this biomarker change did not reduce CV events. Strong ↑ benefit · moderate 2
Prevents cardiovascular events / stroke disabilityLarge RCTs (HOPE-2, VITATOPS) and Cochrane found no reduction in CV events or mortality in replete people. Strong — no effect · negligible 3
Relieves PMS / carpal tunnel symptomsLow-certainty, weak symptom relief; not a substitute for definitive therapy. Preliminary ↔ mixed · small 1
Lung cancer risk from high-dose supplements (male smokers)VITAL cohort linked >20 mg/day individual B6 to ~1.8x higher lung cancer in men, ~3x in male smokers; observational. Preliminary ⚠ risk · moderate 1

Dosing & Compounds

Typical Dose
Adult RDA: 1.3 mg/day (ages 19-50); rising to 1.7 mg/day (men) and 1.5 mg/day (women) over age 50. Typical supplement doses range 1-25 mg/day; therapeutic pregnancy-nausea dosing is 10-25 mg up to 3-4 times daily. US Tolerable Upper Intake Level (UL): 100 mg/day for adults (the more conservative EFSA 2023 UL is 12 mg/day). Doses well above the UL are used short-term only under medical supervision (e.g., isoniazid toxicity).
Active Compounds
Pyridoxine hydrochloride (most common, cheapest supplement and food-fortification form)Pyridoxal-5'-phosphate (P5P/PLP) — the active coenzyme form, marketed as 'pre-activated' though no proven clinical superiority in most peopleFound in multivitamins and combined B-complex/homocysteine formulas with folate + B12Dietary sources: poultry, fish (tuna, salmon), organ meats, chickpeas and other legumes, potatoes and starchy vegetables, bananas, fortified cereals, and nuts

Safety & Cautions

Dietary B6 is non-toxic, but chronic high-dose pyridoxine causes a dose-dependent sensory peripheral neuropathy (ataxia, numbness) — classically reported at 1-6 g/day for months, with some case reports below 500 mg/day; symptoms usually regress on discontinuation. The US UL of 100 mg/day was set with a safety margin (EFSA set 12 mg/day in 2023). A prospective cohort (Brasky 2017, VITAL) linked long-term high-dose individual B6 supplements (>20 mg/d over 10 yr) to nearly doubled lung cancer risk in men (HR ~1.82), with a stronger signal in male smokers; this is an observational association, not proven causation. Key interactions: B6 reduces efficacy of levodopa (when given without carbidopa) and lowers serum levels/efficacy of phenytoin and phenobarbital; isoniazid, hydralazine, cycloserine, and penicillamine antagonize B6 and can cause deficiency. Generally safe in pregnancy at recommended antiemetic doses. Educational only — always check with your doctor or pharmacist before combining Vitamin B6 (Pyridoxine) with any medicine.

Vitamin B6 (Pyridoxine) drug interactions

Known or theoretical interactions between Vitamin B6 (Pyridoxine) and common medications — educational, not exhaustive. Always check with your doctor or pharmacist before combining Vitamin B6 (Pyridoxine) with any medicine.

Caution
Levodopa (without carbidopa)
High-dose B6 can reduce plain levodopa's efficacy; largely prevented when combined with carbidopa.
Pyridoxine accelerates peripheral decarboxylation of levodopa, lowering the amount reaching the brain. NIH ODS — Vitamin B6

Key Studies ★ 11 studies

Cochrane systematic review Martí-Carvajal Cochrane Review 2017 ✓ Full text
Across 15 RCTs, homocysteine-lowering with B6/B12/folic acid did NOT reduce cardiovascular events, MI, or all-cause mortality in people with or without prior CVD.
RCT Field 2026 ✓ PubMed
RCT reported that high-dose vitamin B6 reduced depression symptoms.
clinical guideline ACOG Practice Bulletin 189 (2018) ✓ PubMed
Recommends pyridoxine (vitamin B6) alone or with doxylamine as safe and effective first-line pharmacotherapy for nausea and vomiting of pregnancy.
RCT reanalysis Persaud 2018 reanalysis (PLOS ONE) ✓ Source
Reanalysis of the pivotal doxylamine-pyridoxine (Diclegis) RCT found symptom improvement that did not reach the prespecified minimal clinically important difference, questioning the magnitude of benefit.
large RCT VITATOPS (2010, Lancet Neurology) ✓ PubMed
In 8,164 stroke/TIA patients, B6 25 mg + folic acid + B12 lowered homocysteine but did not significantly reduce the composite of stroke, MI, or vascular death (RR 0.91, 95% CI 0.82-1.00).
large RCT HOPE-2 (Lonn 2006, NEJM) ✓ Source
In 5,522 vascular-disease/diabetes patients, folic acid + B6 50 mg + B12 for ~5 yr did not reduce major CV events; total stroke fell (RR 0.75) but MI and CV death were unchanged.
Review Sielaff 2026 ✓ PubMed
Scoping review of the direct evidence for vitamin B6 depletion during carbidopa/levodopa therapy in Parkinson's disease.
Review Nafea 2026 ✓ PubMed
Vigabatrin-Induced Retinal Toxicity: Unraveling the Gamma-Aminobutyrate-Vitamin B(6) Axis and Metabolic Crosstalk
clinical review Vitamin B6 Toxicity StatPearls (2024) ✓ Full text
Reviews dose-dependent sensory neuropathy from chronic high-dose pyridoxine, generally reversible on discontinuation; basis for the conservative UL.
prospective cohort Brasky 2017 (VITAL cohort, JCO) ✓ PubMed
In >77,000 adults, long-term high-dose individual B6 (>20 mg/d) was associated with ~1.82-fold higher lung cancer risk in men (95% CI 1.25-2.65), and roughly 3-fold in male smokers; no association in women.
authoritative body NIH ODS Fact Sheet (2023) ✓ Source
Authoritative reference: adult RDA 1.3-1.7 mg/day, UL 100 mg/day; chronic pyridoxine 1-6 g/day for 12-40 months can cause severe sensory neuropathy.
11 sources cited · 11 verified Search all studies on PubMed ↗

Common questions about Vitamin B6 (Pyridoxine)

What is Vitamin B6 (Pyridoxine) used for?

Vitamin B6 (Pyridoxine) is most often taken for Corrects deficiency: reverses B6-deficiency anemia, dermatitis, glossitis, neuropathy, and seizures (including isoniazid- or hydralazine-induced and rare pyridoxine-dependent infantile seizures), First-line for nausea/vomiting of pregnancy: pyridoxine 10-25 mg, alone or combined with doxylamine, is recommended by ACOG as safe and effective initial therapy, Lowers plasma homocysteine ~25-30% as part of folic acid + B12 + B6 regimens (a biomarker effect that did NOT translate into fewer cardiovascular events in trials), Prevents isoniazid-induced neuropathy when co-prescribed prophylactically during tuberculosis treatment. The amino-acid and neurotransmitter coenzyme — essential, but a poor supplement for the well-nourished

Does Vitamin B6 (Pyridoxine) work — what does the evidence say?

Strong evidence. Multiple high-quality RCTs / meta-analyses with consistent effects. Vitamin B6, as the active coenzyme pyridoxal-5'-phosphate (PLP), drives over 100 enzymatic reactions, chiefly in amino-acid metabolism, neurotransmitter synthesis (serotonin, GABA, dopamine), heme synthesis, and homocysteine catabolism. Frank deficiency is rare in isolation but causes microcytic anemia, dermatitis, glossitis, peripheral neuropathy, depression, and seizures (classically in isoniazid use, alcoholism, or renal dialysis). In non-deficient people, supplementation has largely failed to deliver clinical benefit: despite lowering homocysteine by roughly 25-30% as part of B6/B9/B12 regimens, large RCTs (HOPE-2, VITATOPS) and a 2017 Cochrane review found no reduction in cardiovascular events or mortality, and a prospective cohort linked high-dose individual B6 supplements (>20 mg/d) to increased lung cancer risk in men, especially smokers. Its best-validated supplemental role is pyridoxine (alone or with doxylamine) as first-line therapy for nausea and vomiting of pregnancy.

What is the typical dose of Vitamin B6 (Pyridoxine)?

Adult RDA: 1.3 mg/day (ages 19-50); rising to 1.7 mg/day (men) and 1.5 mg/day (women) over age 50. Typical supplement doses range 1-25 mg/day; therapeutic pregnancy-nausea dosing is 10-25 mg up to 3-4 times daily. US Tolerable Upper Intake Level (UL): 100 mg/day for adults (the more conservative EFSA 2023 UL is 12 mg/day). Doses well above the UL are used short-term only under medical supervision (e.g., isoniazid toxicity).

Is Vitamin B6 (Pyridoxine) safe? Any cautions or side effects?

Dietary B6 is non-toxic, but chronic high-dose pyridoxine causes a dose-dependent sensory peripheral neuropathy (ataxia, numbness) — classically reported at 1-6 g/day for months, with some case reports below 500 mg/day; symptoms usually regress on discontinuation. The US UL of 100 mg/day was set with a safety margin (EFSA set 12 mg/day in 2023). A prospective cohort (Brasky 2017, VITAL) linked long-term high-dose individual B6 supplements (>20 mg/d over 10 yr) to nearly doubled lung cancer risk in men (HR ~1.82), with a stronger signal in male smokers; this is an observational association, not proven causation. Key interactions: B6 reduces efficacy of levodopa (when given without carbidopa) and lowers serum levels/efficacy of phenytoin and phenobarbital; isoniazid, hydralazine, cycloserine, and penicillamine antagonize B6 and can cause deficiency. Generally safe in pregnancy at recommended antiemetic doses.

How many studies support Vitamin B6 (Pyridoxine)?

NutriDex cites 11 sources for Vitamin B6 (Pyridoxine), graded "Strong".

Does Vitamin B6 (Pyridoxine) interact with any medications?

Yes — known or theoretical interactions include: Levodopa (Parkinson's) (caution). This is educational and not exhaustive; always check with your doctor or pharmacist before combining Vitamin B6 (Pyridoxine) with any medicine.

Cite this page
APA

Peh, D. (2026). Vitamin B6 (Pyridoxine) (Pyridoxine / P5P): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/vitamin-b6

BibTeX
@misc{nutridex_vitamin_b6,
  author       = {Peh, Daryl},
  title        = {Vitamin B6 (Pyridoxine) (Pyridoxine / P5P): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/vitamin-b6},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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