Compound or practice · Supplement
Vitamin B6
A cofactor for neurotransmitter and amino-acid metabolism; genuinely useful for pregnancy nausea and PMS, toxic if chronically megadosed.
- Overall grade
- Grade B
- Last revised
- 3
- graded outcomes
- 0
- references listed
A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.
3 at grade B — 3 graded rows
What is known
Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.
- Pregnancy nauseaEvidence grade B
Often with doxylamine
Moderatehigh
- PMS symptomsEvidence grade B
Modest benefit
Smallmixed
- HomocysteineEvidence grade B
With folate/B12
Smallhigh
What is uncertain
Read off the same rows as above. Nothing here is added that the entry does not itself record.
- Studies disagree: PMS symptoms (mixed agreement).
Interactions
Documented pairings with supplements and medicines. A medicine on this list is a conversation for whoever prescribes it.
MagnesiumWorks together
Common PMS pairing; complementary mechanisms.
The evidence in words
What it is
B6 is a water-soluble vitamin whose active form, pyridoxal-5-phosphate (P5P), is a cofactor for over a hundred enzymes, especially those handling amino acids and neurotransmitters. Frank deficiency is uncommon but subclinical low status occurs.
How it works
P5P is the coenzyme for transaminases and decarboxylases that build serotonin, dopamine, GABA, and heme, and that clear homocysteine via the transsulfuration pathway. Its neurotransmitter roles underlie its use in nausea and premenstrual symptoms.
What the evidence shows
Reasonable evidence supports B6 for nausea and vomiting of pregnancy (often combined with doxylamine) and modest relief of premenstrual symptoms. It contributes to homocysteine control alongside folate and B12. Broader mood and 'nerve health' claims are weaker. Crucially, chronic high-dose B6 (typically above ~200 mg/day for long periods) causes a reversible sensory neuropathy — a rare example of a water-soluble vitamin with real overdose toxicity.
How to use it
10–25 mg/day covers supplemental needs; pregnancy nausea protocols use 10–25 mg a few times daily under care. Do not chronically exceed ~100 mg/day without reason.
Safety & interactions
Safe at low doses; chronic megadosing causes peripheral neuropathy that resolves slowly on stopping. Respect the upper limit. Magnesium — Common PMS pairing; complementary mechanisms.
Bottom line
Useful and cheap for pregnancy nausea and PMS at modest doses, and a homocysteine cofactor — but this is the water-soluble vitamin to not megadose, because sustained high intakes damage sensory nerves.
How it is used
As the entry records it, from the studies it summarises. Not a recommendation for you — doses that suit a trial population may not suit you.
- Standard
- 10–25 mg/day; avoid chronic >100 mg.
Goes with
- MagnesiumCommon PMS pairing; complementary mechanisms.Evidence grade B
Questions people ask
Is more better for mood?
No — and it's actively risky. Sustained high doses cause a sensory neuropathy. Stay near the requirement unless a clinician directs otherwise.
Related reading
Entries that share this one's tags or conditions.
- Vitamin B6 for HomocysteineEvidence grade B — With folate/B12Evidence grade B
- Vitamin B6 for PMS symptomsEvidence grade B — Modest benefitEvidence grade B
- Vitamin B6 for Pregnancy nauseaEvidence grade B — Often with doxylamineEvidence grade B
- Vitamin B6: dosage and how to take it10–25 mg/day; avoid chronic >100 mg.Evidence grade B
Sources
This entry lists no references of its own.
Last revised . A grade is this entry's reading of the evidence, not medical advice.