Vitamin B6 (Pyridoxine)

Vitamin B6 (pyridoxine) is a water-soluble vitamin. It helps more than 100 enzymes in the body, most of them handling protein and amino acids. That is according to the NIH (the US National Institutes of Health). The name covers six related compounds, and pyridoxal 5′-phosphate (PLP) is the form that does the work.

Adults need about 1.3 to 1.7 mg a day, a few thousandths of a gram. It is one of the B vitamins, and it works alongside folate and vitamin B12.

Here is the part most people do not know: about three quarters of your body’s B6 sits in muscle. Most of it is bound to an enzyme that releases glucose from stored glycogen, says EFSA (the EU’s food safety agency).

The name dates from the 1930s. Paul György showed that a factor curing a skin disease in rats was vitamin B6. He later proposed the name pyridoxine for its chemical structure.

B6 is unusual: the safety question is about too much, not too little. Deficiency from diet alone is uncommon, but long-term high-dose supplements can damage sensory nerves. The EU’s upper limit is 12 mg a day and the US limit is 100 mg a day. Part of the reason is that the two panels weighed older case reports differently.

Health benefits of vitamin B6

• ★★★EU allows ten claims for normal body functionsFoods that are a source of vitamin B6 may say it contributes to normal energy metabolism, the nervous system, immune function and less tiredness. These are function claims, not treatment claims.
• ★★★No change in heart attacks or deathsSupplements of B6, folic acid or B12, alone or combined, did not change heart attacks or deaths from any cause across 15 trials (71,422 people). B6 alone at 40 mg a day also left deaths and heart events unchanged in one trial of 3,096 people.
• ★★★Barely any change in thinking skillsSupplements of folic acid, B12 or B6, alone or combined, changed thinking scores only a tiny amount in 27,882 healthy adults, mostly over 60. In two small trials of healthy older people, B6 alone did not improve mood or thinking.
• ★★Less nausea in early pregnancyIn 342 women, 30 mg of B6 a day lowered nausea scores more than a placebo over 5 days. A Cochrane review found only limited evidence for B6 and other treatments for mild or moderate symptoms.
• ★★More relief from premenstrual symptomsAcross nine placebo-controlled trials of 940 women, B6 gave more than double the odds of improvement in overall symptoms (2.32 times). Most trials were low quality, and 100 mg a day, the top dose used, is above the EU upper limit of 12 mg.

Foods high in vitamin B6

B6 is found in many foods, and in our USDA ranking per serving, animal foods and potatoes lead. A 4 oz (113 g) serving of chicken breast has 0.92 mg, 54% of the 1.7 mg Daily Value (the FDA label value). Tuna follows with 0.72 mg per 3 oz (85 g), then wild Atlantic salmon with 0.7 mg per 3 oz. Potatoes give 0.63 mg per medium potato (213 g).

Farmed Atlantic salmon, pistachio nuts, chicken drumstick, mackerel, bananas and soybeans complete the top 10; the ranking below gives their amounts. Per 100 g the order changes: pistachio nuts lead with 1.7 mg, then sunflower seeds (1.35 mg) and garlic (1.24 mg). But the serving size matters for what you actually eat.

The NIH table adds foods that are not in the top 10 of our ranking. Canned chickpeas give 1.1 mg per cup (65% of the Daily Value) and pan-fried beef liver 0.9 mg per 3 oz. A breakfast cereal fortified with 25% of the Daily Value gives 0.4 mg.

US adults get most of their B6 from fortified cereals, beef, poultry, starchy vegetables and some non-citrus fruits, the NIH says. About 75% of the B6 in a mixed diet is absorbed.

Plants carry part of their B6 as pyridoxine glucoside. In isotope studies, people use it about half as well as pyridoxine. One 18-day feeding study in nine women tested this. With 27% of the diet’s B6 as the glucoside, B6 markers were 10% to 18% lower than on a diet with 9%.

EFSA adds that heating lowers the availability of B6 in animal foods by 25% to 30%. The reason is that pyridoxal and PLP react with the amino acid lysine. We found no measured cooking losses for individual foods that we could cite. So treat any single percentage you see with care.

How vitamin B6 works

The biochemistry below is well established. But it comes from official reports and physiology studies, not from trials of B6 pills, and the toxicity mechanism comes mostly from cells.

Four ideas cover most of it. PLP helps more than 100 enzymes, and one of its jobs is to move homocysteine on to cysteine. The body keeps most of its B6 in muscle, and at high doses blood levels stop rising while pyridoxine itself builds up. Then comes what has been seen in people.

It is a helper for more than 100 enzymes

PLP is a coenzyme (a helper molecule) for more than 100 enzymes, most of them in amino acid metabolism, says the Institute of Medicine. EFSA explains what these enzymes do. They move amino groups from one molecule to another, and turn amino acids into their mirror forms. They also strip carboxyl groups off amino acids to make signaling amines such as serotonin, dopamine and GABA.

PLP also runs the first step of making heme, the iron-holding part of hemoglobin. That is why a shortage gives small, pale red blood cells (microcytic anemia). In muscle and liver, PLP is part of glycogen phosphorylase, the enzyme that frees glucose from glycogen. The nerve signs of deficiency are tied to lower GABA and to a build-up of tryptophan breakdown products that can provoke seizures, EFSA says.

It moves homocysteine on to cysteine

Homocysteine, an amino acid in blood, has two routes. In one, a methyl group from folate turns it into methionine, a reaction that also needs vitamin B12. In the other, called transsulfuration, two PLP enzymes (cystathionine β-synthase and cystathionine γ-lyase) turn it into cysteine, EFSA says. PLP also helps run the one-carbon reactions that feed the folate cycle.

That is why B6 was tried in homocysteine trials, and why the EU allows the claim “normal homocysteine metabolism”. But lowering homocysteine with B vitamins did not prevent heart attacks or deaths in a Cochrane review of 15 trials. That review is among the study cards.

Most of it sits in muscle, and the rest leaves in urine

About 75% to 80% of your body’s B6 is in muscle, including the heart, bound to glycogen phosphorylase. Another 5% to 10% is in the liver, EFSA reports.

That muscle pool is not a reserve for the rest of the body. In young men, muscle B6 hardly changed over 6 weeks on a restricted diet. It also hardly changed over the next 6 weeks on 164 mg a day of extra B6.

The Institute of Medicine cites estimates of body stores: about 61 mg in a young woman and 110 mg in a young man. These stores have a half-life of about 25 days. It says these may be underestimates because muscle turns over slowly, and notes that B6 is not stored to any substantial extent.

The main waste product is 4-pyridoxic acid in urine. At very high doses, much of the pyridoxine is excreted unchanged, the Institute of Medicine says.

Blood levels stop rising at high doses, and pyridoxine itself builds up

PLP travels in blood bound to albumin, a blood protein, and the binding has a limit. At high intakes, the enzymes that make PLP also saturate (work at full capacity). So blood PLP levels off, and free pyridoxal becomes the main form in plasma (the liquid part of blood). Pyridoxine itself, normally absent, starts to appear, EFSA says in its 2023 opinion.

EFSA summarizes one study of pyridoxine hydrochloride at 10 to 800 mg a day for 1 week. Every dose gave a similar plasma PLP of around 600 nmol/L. Without a supplement it was around 70 nmol/L. Other forms rose from 100 mg a day.

In cultured cells, only pyridoxine lowered cell survival, and it blocked two PLP enzymes, which suggests it competes with the active form. A 2021 review weighs the cause of the nerve damage. Blocked pyridoxal kinase and disturbed GABA signaling in sensory nerves is the most plausible cause, it concludes, but the mechanism is still unproven.

What has been seen in people

The human findings are mostly about intake, status and harm. Most US adults reach the RDA (the US recommended daily amount). But survey data show a low blood PLP in many young women, smokers and others at typical intakes. B6 pills raise blood PLP, as seen in older men, yet did not improve mood or memory.

Together with folic acid and B12, B6 lowered homocysteine without preventing heart attacks. In pregnancy, small trials found less nausea with 30 mg of pyridoxine, though a Cochrane review calls the evidence weak. The clearest risk is nerve damage from long-term high doses. All of these are among the study cards.

How much vitamin B6 do you need?

Adults aged 19 to 50 need 1.3 mg of vitamin B6 a day, according to the US recommended dietary allowance (RDA). From age 51 the RDA is 1.7 mg for men and 1.5 mg for women. It is 1.9 mg in pregnancy and 2.0 mg while breastfeeding.

In the EU, EFSA’s population reference intake (an amount that covers nearly everyone) is 1.6 mg for women and 1.7 mg for men. It is 1.8 mg in pregnancy and 1.7 mg when breastfeeding.

The values differ a little because the panels used different blood targets. The US panel aimed for a plasma PLP of at least 20 nmol/L. EFSA used a population mean of 30 nmol/L, the traditional marker of adequate status. It found no conclusive evidence that B6 needs change with protein intake in the range eaten in Europe.

The Institute of Medicine thought the need rises by about 0.2 to 0.3 mg after age 50. It said the need may be higher on very high-protein diets. In pregnancy it estimated an extra 0.25 mg a day. It noted that blood PLP drops in pregnancy, and that it is not clear whether this reflects poorer status or a normal change.

In the US, babies have an adequate intake (AI) of 0.1 mg from birth to 6 months and 0.3 mg from 7 to 12 months. An AI is used when there is too little data for an RDA; these values come from the intake of healthy breastfed babies.

Intakes are close to the targets for many people. US adults eat about 1.5 mg a day (women) and 2 mg (men), according to the NIH. In the 2003 to 2004 national survey, 11% of B6 supplement users had a plasma PLP below 20 nmol/L, and 24% of non-users. Lower levels were more common in women, smokers and underweight people.

The survey’s authors found that intakes of 2 to 2.9 mg a day still left more than 3% with a low PLP in every group. Most users of oral contraceptives (birth control pills) had a PLP below 20 nmol/L. The authors concluded that 3 to 4.9 mg a day looked consistent with an RDA for most Americans.

A low blood level is not the same as deficiency symptoms. The Institute of Medicine says those symptoms have never been seen at intakes of 0.5 mg a day or more.

Vitamin B6 deficiency: signs and who is at risk

Deficiency is uncommon and usually shows up with low levels of other B vitamins, according to the NIH. The signs are microcytic anemia, abnormal brain-wave tracings, depression, confusion and weaker immunity. Another is a scaly rash with cracked lips and a swollen tongue (dermatitis with cheilosis and glossitis). In infants, it causes irritability, unusually acute hearing and seizures.

People with borderline status may have no signs for months or years. In the early 1950s in the USA, babies were fed a formula that was low in B6 because of a manufacturing error. They developed anemia, failed to thrive and had convulsive seizures, EFSA reports.

The NIH lists the groups most at risk. They include people with kidney disease, dialysis or a transplant, and people with alcohol dependence. Others have an autoimmune disease such as rheumatoid arthritis, celiac disease, Crohn’s disease or ulcerative colitis.

Blood PLP is also often low in people with obesity and in pregnancy. Some seizure medicines (such as valproic acid, carbamazepine and phenytoin) speed up B6 breakdown. Smokers and women on oral contraceptives had low PLP in the national survey.

The usual test is plasma PLP. Values of more than 30 nmol/L have been the traditional marker of adequacy, and the US panel used 20 nmol/L. Inflammation lowers plasma PLP through lower albumin and higher alkaline phosphatase, EFSA says. So a low value in someone who is ill may not mean a lack of B6 in the diet.

In people with rheumatoid arthritis, B6 supplements normalized the level but did not lower inflammatory markers, the NIH reports. Treating a true deficiency is a doctor’s call.

Forms of vitamin B6: absorption and effects

Vitamin B6 supplements mostly contain pyridoxine hydrochloride, the NIH says, although some contain pyridoxal 5′-phosphate (P5P). The body converts every form to PLP, so all of them count as vitamin B6. The NIH says absorption from supplements does not differ substantially among forms.

EFSA puts the absorption of pyridoxine hydrochloride at about 95%. Phosphate forms lose their phosphate in the gut first and are absorbed as pyridoxal.

The honest bottom line: P5P is marketed as the “active” form. But we found no trial that compared it with pyridoxine for absorption in deficiency, for health outcomes or for safety. The reports behind the US upper limit involved pyridoxine, the form the Institute of Medicine reviewed. In cell tests, pyridoxine was the only form that lowered cell survival.

Yet EFSA applies its upper level to every form, and asks for research on differences in toxicity between forms. It also notes that free pyridoxine can appear in the blood of some people after PLP supplements. Until trials exist, the dose matters more than the form.

Form	Activity or conversion	What studies show	Source
Pyridoxine hydrochloride	Converted to PLP in the liver. The most common form in supplements. About 95% is absorbed.	Named in the nausea trial (30 mg a day) and in the trial in older men (20 mg a day, which raised blood PLP but did not change mood or memory). In cells it was the only form that lowered cell survival. EFSA’s upper level covers it like every other form.	1, 2, 3, 9, 11, 12
Pyridoxal 5′-phosphate (P5P or PLP)	The active coenzyme. The gut removes the phosphate before the vitamin is absorbed.	No trial we found compared it with pyridoxine for health outcomes. A Cochrane review of three small trials found milder tardive dyskinesia than placebo, with low-quality evidence. EFSA lists a small uncontrolled case series in which five people with neuropathy symptoms improved after switching from a B6 supplement to P5P, which cannot show that P5P is safer.	1, 3, 8
Pyridoxamine and pyridoxal	Converted to PLP in the body.	In a crossover study of five men, equal doses of pyridoxine, pyridoxal and pyridoxamine gave similar rises in blood PLP. EFSA agreed that differences between forms reflected metabolism, not absorption.	2
Pyridoxine glucoside (plant foods)	A sugar-bound form that must be split in the gut.	About 50% to 58% as available as pyridoxine in isotope studies in people, and it slowed the use of pyridoxine taken with it. It makes up roughly 15% of B6 intake in an average diet.	2, 3, 6, 7
B6 in a mixed diet	About 75% as available as pyridoxine in a supplement.	A feeding study found 71% to 79%. EFSA counts 1 mg of B6 from food as equal to 0.8 mg of pyridoxine hydrochloride from a supplement.	1, 3, 5

In a single-dose study, 20 older adults had lower blood pyridoxine and PLP over 4 hours after a multivitamin than 20 younger adults. The authors say this may mean altered absorption or conversion with age. Here are the form-specific studies, 3 in all, strongest evidence first.

Is vitamin B6 safe? Supplements, dose and interactions

Vitamin B6 from food has not been reported to cause harm, according to the NIH and the Institute of Medicine. The risk comes from supplements, and the two main panels set very different upper limits.

The US Tolerable Upper Intake Level (UL, the most you should take each day) is 100 mg a day for adults. It counts pyridoxine from food and supplements together. It is 80 mg for ages 14 to 18, and lower for children. It does not apply to people treated for a medical reason under a doctor’s care.

EFSA’s 2023 upper level is 12 mg a day for adults, including pregnant and breastfeeding women. It covers all dietary sources and all forms of B6. For infants from 4 months and children it is 2.2 to 10.7 mg. The EU’s earlier committee had set 25 mg in 2000.

The gap comes from how the panels read the same older reports. The US panel took studies in patients with carpal tunnel syndrome or diabetic neuropathy. From them it set a no-effect level of 200 mg a day, then halved it. It judged a case-control study of women with premenstrual syndrome not reliable enough to use.

EFSA used that study: neuropathy symptoms were reported by 48% of women taking under 50 mg for more than 6 months. Case reports and national vigilance data supported it. EFSA took 50 mg a day as a reference point, divided it by 4, and checked the result against a dog study.

• Nerve damage. Taking 1 to 6 g a day for 12 to 40 months can cause severe, progressive sensory neuropathy with loss of coordination, the NIH says. The symptoms usually stop after the supplement is stopped. EFSA concluded that symptoms may occur at 50 mg a day and below, with large differences between people. In 90 Dutch reports, products with 1.4 to 100 mg of B6 were plausibly linked to neuropathy. Australia’s regulator announced in November 2025 that some products will be pharmacist-only from June 2027. They are those with more than 50 and up to 200 mg per daily dose. It cited 250 neuropathy reports up to the end of October 2025, according to RACGP newsGP. Other effects at high doses include skin lesions, sensitivity to sunlight, nausea and heartburn.
• Pregnancy. ACOG is the US college of obstetricians. It recommends 10 to 25 mg of B6 three or four times a day for nausea and vomiting in pregnancy, the NIH says. Doxylamine can be added if that is not enough. Pregnant women should talk to a doctor first, because such doses could approach the US limit. EFSA found no sign that pregnancy raises sensitivity, and three case-control studies found no higher risk with up to 60 mg a day. One covered about 23,000 babies with birth defects and 38,000 without. The Institute of Medicine notes that very high doses (600 mg a day by mouth) were used to suppress milk production. Trial results conflicted, and no such effect was found at lower doses.
• Cancer and bones. In one cohort, men taking more than 20 mg a day from individual supplements for 10 years had almost twice the lung cancer risk. In long follow-up of two trials, B6 went with more hip fractures. Both are observational or secondary findings that cannot prove cause, and the Norwegian trials of B6 found no clear effect on cancer. Higher blood PLP went with less colorectal cancer in cohorts.
• Medicines. Some seizure medicines (valproic acid, carbamazepine, phenytoin) lower blood PLP. In some research, 200 mg a day of pyridoxine lowered blood levels of phenytoin and phenobarbital, the NIH says. Theophylline, an asthma medicine, also lowers PLP. The antibiotic cycloserine increases urinary loss of pyridoxine, and pyridoxine supplements can help prevent its seizures and nerve toxicity. The Institute of Medicine adds that isoniazid and L-DOPA have been reported to lower plasma PLP.
• Who should ask a doctor. Anyone who is pregnant and considering B6, and anyone with kidney disease. Also anyone on seizure, tuberculosis or asthma medicines, and anyone with tingling or numbness in the hands or feet while taking B6. Stacking is the quiet risk: a multivitamin, a B-complex and a mood or sleep blend can each carry B6. Add the labels up and compare the total with the limits above.

How to get more vitamin B6

• Eat B6 foods through the week. In our ranking, chicken breast gives 0.92 mg per 4 oz, tuna 0.72 mg per 3 oz and wild Atlantic salmon 0.7 mg. A medium potato gives 0.63 mg and a medium banana 0.43 mg, and the NIH lists canned chickpeas at 1.1 mg per cup. About 75% of the B6 in a mixed diet is absorbed.
• If you eat few of these, check fortified cereals. The NIH says US adults get much of their B6 from fortified cereals. A cereal fortified with 25% of the Daily Value gives 0.4 mg a serving. Read the label for the amount.
• Think twice before a high-dose pill. Food does not reach harmful amounts, and the daily need is 1.3 to 1.7 mg. The Institute of Medicine notes that over-the-counter B6 is sold at doses up to 100 mg or more. Compare the label with the EU limit of 12 mg, and ask a doctor if you are unsure.

History of vitamin B6

The story starts with sore skin in rats. In the 1930s, Rudolf Peters fed young rats a purified diet with added thiamin and riboflavin. They developed severe skin lesions, which he called rat acrodynia. In 1934 Paul György showed that the factor curing it was vitamin B6.

Other work soon found that a lack of it also caused convulsions in rats, pigs and dogs, and a small-cell anemia in some animals. Samuel Lepkovsky isolated and crystallized the vitamin in 1938.

In 1939 Leslie Harris and Karl Folkers, and separately Richard Kuhn with colleagues, showed that it was a pyridine derivative. György then proposed the name pyridoxine. In 1942 Esmond Snell developed a growth test with microbes that led to the discovery of pyridoxamine and pyridoxal. These three forms have largely equal activity, because the body converts them into the active coenzyme, pyridoxal 5′-phosphate.

The first report of nerve damage from megadoses came much later. A 1983 case series described seven adults with severe sensory nerve damage after 2 to 6 g of pyridoxine daily, says the Institute of Medicine. Yet pyridoxine toxicity had been documented in animals since 1940. The Institute of Medicine also cites a 1954 report of convulsive seizures in infants fed a pyridoxine-deficient diet.

Frequently asked questions about vitamin B6

How much vitamin B6 is too much per day?

It depends on who sets the limit. EFSA’s upper level is 12 mg a day for adults, from food and supplements together and covering every form of B6. The US limit is 100 mg a day for adults, set from older studies. Nerve damage was first reported at 2 to 6 g a day, but EFSA concluded symptoms may occur at 50 mg a day and below. Dutch reports of nerve problems involved products with 1.4 to 100 mg per tablet, so doses under 50 mg a day could not be excluded. The Institute of Medicine notes that over-the-counter B6 is sold at doses up to 100 mg or more. So check labels and add up every product. Food does not reach harmful amounts.

Does vitamin B6 help with pregnancy nausea?

Possibly a little. In a trial of 342 women, 30 mg of pyridoxine a day lowered nausea scores more than placebo over 5 days. But a Cochrane review of 41 trials found only limited evidence for B6, and no strong evidence for any treatment. The NIH says ACOG recommends 10 to 25 mg three or four times a day, with doxylamine added if needed. Pregnant women should talk to a doctor first, because such doses could approach the US limit. The US limit is not meant to apply to people treated under close medical supervision.

What is the difference between pyridoxine and P5P?

Pyridoxine is the usual supplement form. Pyridoxal 5′-phosphate (P5P or PLP) is the active coenzyme, and the body converts every form into it. The NIH says absorption does not differ substantially among supplement forms. We found no trial comparing P5P with pyridoxine for health outcomes or safety. So claims that P5P works better or is safer have no trial behind them. EFSA’s upper level covers every form.

Which foods are highest in vitamin B6?

In our USDA ranking per serving, chicken breast leads with 0.92 mg per 4 oz. Next come tuna (0.72 mg per 3 oz), wild Atlantic salmon (0.7 mg), potatoes (0.63 mg per medium potato) and farmed Atlantic salmon (0.54 mg). Per 100 g, pistachio nuts lead with 1.7 mg, then sunflower seeds (1.35 mg) and garlic (1.24 mg). The NIH table adds canned chickpeas at 1.1 mg per cup. About 75% of the B6 in a mixed diet is absorbed.

Does vitamin B6 help with premenstrual syndrome?

It may, but the evidence is weak. A review pooled nine placebo-controlled trials in 940 women. With B6 up to 100 mg a day, the odds of overall improvement were 2.32 times those on placebo. The authors said most trials were of low quality. That dose is far above EFSA’s 12 mg upper level. EFSA notes the first reports of B6 nerve damage came mainly from women taking it for premenstrual symptoms. So talk to a doctor before trying high doses.

Can vitamin B6 lower homocysteine and protect your heart?

B6 is part of the homocysteine pathway, but protection has not been shown. In a Cochrane review of 15 trials with 71,422 people, homocysteine was lowered with B6, folic acid or B12. Heart attacks (1.02 times the risk) and deaths (1.01 times) did not change. In the Norwegian trials, B6 alone did not clearly change events (0.90 times the risk in one, 1.14 times in the other). Strokes were slightly fewer in the Cochrane review (4.3% against 5.1%), but those trials gave the vitamins in mixes.

Does vitamin B6 help with anxiety, depression or memory?

The evidence is limited. In a one-month trial of 478 young adults, high-dose B6 lowered self-reported anxiety. But it was short, and the report calls the dose only high. A systematic review found no clear effect on depression overall. A Cochrane review of two trials in 109 healthy older people found no gain in mood or thinking from B6. A larger Cochrane review found B vitamins probably have little or no effect on thinking skills in healthy adults.