Vitamin B6 (P5P / Pyridoxine)

pyridoxine · pyridoxal-5-phosphate · P5P · pyridoxal phosphate · vitamin B6

Snapshot

Indications	Contraindications
Nausea/vomiting in pregnancy^1–3 Premenstrual syndrome⁴ Migraine with aura prophylaxis⁵ Levetiracetam-induced NPAEs⁶ Isoniazid-induced neuropathy⁷ Pyridoxine-dependent epilepsy⁸ B6 deficiency states⁴	Chronic high-dose pyridoxine use⁹

Vitamin B6 (pyridoxine, pyridoxal, pyridoxamine, and their phosphate esters) serves as a cofactor in more than 100 enzyme reactions, with pyridoxal 5'-phosphate (PLP) as the active coenzyme form, participating in amino acid metabolism, neurotransmitter biosynthesis, homocysteine regulation, and gluconeogenesis⁴. Supplementation is used for nausea and vomiting of pregnancy (NVP), premenstrual syndrome (PMS), migraine with aura (MA) prophylaxis, and as an adjunct for levetiracetam-induced neuropsychiatric adverse events (NPAEs), with the neurotransmitter-synthesis role driving the mood and emesis applications⁴. Patients most likely to present with inadequate status include those with alcohol dependence, renal insufficiency, inflammatory bowel disease, and rheumatoid arthritis⁴.

For NVP, a 2023 systematic review and meta-analysis of 18 trials found pyridoxine supplementation alone and in combination significantly improved nausea scores¹. The American College of Obstetrics and Gynecology (ACOG) recommends pyridoxine monotherapy as initial management for NVP, with doxylamine added if response is insufficient⁴. For PMS, a meta-analysis found benefit over placebo, though most contributing trials were small with methodological limitations⁴. For MA prophylaxis, a 2020 systematic review identified significant benefit of B6 alone or combined with folate in five randomized controlled trials (RCTs)⁵. A 2024 in vitro and animal study found that pancreatic ductal adenocarcinoma (PDAC) cells suppress natural killer (NK)-cell cytotoxicity by depleting vitamin B6 in the tumor microenvironment, with no human trial yet testing this mechanism¹⁰. Products are available as pyridoxine hydrochloride and PLP in capsules, tablets, and powders, with over 58,000 products listing vitamin B6 in commercial databases; see Form comparison.

The most consequential safety signal is sensory neuropathy with sustained high-dose pyridoxine use; symptom severity is dose-dependent and generally resolves after discontinuation, per the NIH Office of Dietary Supplements (ODS) fact sheet⁴. Antiepileptic medications including valproic acid, carbamazepine, and phenytoin accelerate B6 catabolism, while pyridoxine at high doses may reduce phenytoin and phenobarbital serum concentrations, a pharmacokinetic interaction that ODS identifies as requiring attention from prescribers managing these medications⁴.

Last updated October 7, 2026. Read how we make monographs.

In the full monograph

72 sources, 53 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources