Vitamin B6 benefits

How is the role in the body separated from the benefit of a supplement?

Vitamin B6 takes part in amino acid metabolism, hemoglobin formation and immune function as a coenzyme of many enzymes. These roles do not mean that additional B6 will improve these processes in a person without deficiency. Benefit claims divide into three different questions: correcting a deficiency, having a therapeutic effect in a specific condition, and reducing disease risk. ^[1]

It is also misleading to evaluate benefit separately from safety information: EFSA reports that regular high B6 intake can cause peripheral neuropathy and has set the upper limit for adults at 12 mg/day. The amounts used in some of the studies below are far above this limit. ^[8]

What does B6 correct in deficiency?

StatPearls states that B6 deficiency is rare but can be seen together with certain diseases, medications, inadequate nutrition and inherited metabolic disorders; that pyridoxine is used therapeutically in B6-dependent syndromes, in some poisoning emergencies and in pregnancy nausea. The NIH reports that end-stage kidney disease and chronic kidney failure, and malabsorption disorders such as celiac disease, Crohn’s disease and ulcerative colitis, can lead to B6 deficiency. ^{[2] [1]} The clinical picture of deficiency is microcytic anemia, dermatitis (itchy rash), cracks at the lips and corners of the mouth, swollen tongue, depression and confusion, weakened immune function, and in infants irritability, excessive sensitivity to sound and seizures. According to the NIH, people with borderline or mild deficiency may have no symptoms for months or even years. ^[1]

These pictures are associated with B6 deficiency; however, the same symptoms have other causes, and it has not been shown that a supplement would correct these symptoms in a person without deficiency. Details are on the deficiency symptoms page.

Is B6 recommended for nausea in pregnancy?

The NIH reports that about half of pregnant women have nausea and vomiting in the early months and 50–80% have nausea alone; that the condition is not life-threatening and mostly resolves between 12 and 20 weeks. ^[1]

The ACOG’s 2018 Practice Bulletin 189 (reaffirmed in 2024) states that mild cases may improve with dietary and lifestyle changes and that safe and effective treatments exist for more severe cases; in drug treatment it considers pyridoxine (B6) alone or together with doxylamine safe and effective. According to the NIH’s relay, the ACOG recommends B6 alone first, and adding doxylamine if there is no improvement. This is a guideline recommendation; the amount, frequency and when to start are determined by a physician and are not given on this page. ^{[3] [1]}

The guideline is specific to pregnancy; use of B6 for nausea outside pregnancy cannot be inferred from this recommendation. EFSA’s 2023 upper limit also covers pregnant and breastfeeding women (12 mg/day). ^[8]

Does B6 work in premenstrual syndrome (PMS)?

The 1999 systematic review by Wyatt and colleagues examined published randomized controlled studies comparing B6 with placebo in premenstrual syndrome; 9 studies (940 women) entered the analysis. With all nine studies, improvement over placebo in overall premenstrual symptoms was OR 1.57 (95% CI 1.40–1.77); when one study causing significant heterogeneity was removed, OR 2.32 (1.95–2.54) was found, and this second value was given in the abstract. For depressive symptoms, again after one heterogeneous study was left out, OR 1.69 (1.39–2.06) was found with the remaining 4 studies and 541 patients. ^[4]

The authors stated that the results were limited by the low quality of most studies and that the response was not dose-dependent; in the conclusion section they mentioned doses of up to 100 mg per day. This amount is far above EFSA’s 12 mg/day upper limit; it is not a usage recommendation. The review ends by saying that a randomized study of adequate power and good quality is needed. ^[4] For this reason, the result is not sufficient to say “B6 treats PMS”; the level of evidence is low.

One more point needs attention: the case-control study on which EFSA based the upper limit in 2023 involved 172 women using B6 for PMS, and neurological symptoms were reported in 103 of them (60%). That is, the amounts used for PMS are also the amounts for which the most safety data have been collected. ^[8]

Does B6 work in carpal tunnel syndrome?

The 2004 systematic review by Goodyear-Smith and Arroll examined the non-surgical management of carpal tunnel syndrome (2 systematic reviews, 16 randomized studies and 1 before-and-after study). It was stated that a significant proportion of carpal tunnel cases resolve on their own and that there was strong evidence that local corticosteroid injection, and to a lesser extent oral corticosteroid, provides short-term relief. The evidence did not support the use of non-steroidal anti-inflammatory drugs, diuretics, pyridoxine (B6), chiropractic treatment and magnet therapy. ^[5]

The review states that the first studies were promising but that more recent randomized studies did not show clinical improvement over placebo, and that the studies were small. The review is from 2004, and no benefit has been shown for B6 in carpal tunnel.

Does B6 improve memory and mood?

The 2003 Cochrane review looked at double-blind randomized studies comparing B6 with placebo. No studies were found in people with cognitive impairment or dementia. The two included studies had 109 healthy older people in total: one with women only (in a 5-week multi-arm study, 12 women aged 65–92 received B6 and 21 women received placebo), the other with 76 men aged 70–79 (12 weeks). No significant difference in mood or cognitive function was found in either. The review reported no evidence of a short-term benefit, but that more randomized studies are needed. ^[6]

This result rests on two very small, short-term (5 and 12 weeks) studies; it does not lead to the conclusion that “B6 is harmful to memory” or “has no effect in the long term.” It says only that no reliable evidence exists for a benefit of the supplement on cognitive function.

Does B6 lower homocysteine and prevent cardiovascular disease?

Because B6, B12 and folic acid take part in homocysteine metabolism, these vitamins have been tried together on the assumption that high homocysteine is a cardiovascular risk. The 2017 update of the Cochrane review pooled 15 randomized studies (71,422 participants) followed for at least one year; patients with end-stage kidney failure were excluded. The intervention was giving B6, B9 or B12 supplements singly or together. ^[7]

Compared with placebo, there was no difference in heart attack (RR 1.02; 0.95–1.10; 12 studies, 46,699 people), all-cause death (RR 1.01; 0.96–1.06; 11 studies) and serious adverse events (RR 1.07; 1.00–1.14). Stroke showed a small reduction (RR 0.90; 0.82–0.99; 10 studies, 44,224 people). These results do not separate the effect of B6 alone; the comparison of high and low doses also remained uncertain. ^[7]

Evidence summary: result, population and limit

How does the expectation of benefit translate into a decision on use?

The purpose of use is decisive: treating a deficiency, offsetting the effect of a drug interaction, or a general health expectation are separate questions. In a person without deficiency, the benefit of a supplement is limited; on the safety side, the NIH/IOM upper limit (100 mg/day) and the EFSA 2023 upper limit (12 mg/day) differ greatly from each other. Details are in the main guide. This page does not recommend an amount. ^[8]