Vitamin B6

A water-soluble B vitamin involved in more than 100 enzyme reactions, mostly in protein metabolism. Fish, organ meats, potatoes and fortified cereals are rich sources.

How much you need

The official Recommended Dietary Allowance for adults, per day:

Age	Men	Women	Pregnancy	Breastfeeding
19–50 years	1.3 mg	1.3 mg	1.9 mg	2 mg
51–70 years	1.7 mg	1.5 mg	—	—
Over 70	1.7 mg	1.5 mg	—	—

People aged 18 fall in the official 14–18 group — 1.3 mg a day for males and 1.2 mg for females, 1.9 mg in pregnancy and 2.0 mg when breastfeeding. Its upper limit is lower, at 80 mg. Pregnancy and breastfeeding change what you need — confirm yours with your midwife, obstetrician or doctor.

Upper limit

Age	Men	Women	Pregnancy	Breastfeeding
19–50 years	100 mg	100 mg	100 mg	100 mg
51–70 years	100 mg	100 mg	—	—
Over 70	100 mg	100 mg	—	—

The upper limit covers vitamin B6 from food and supplements combined. It is the most that is unlikely to cause harm, not a target. It was set to guard against nerve damage, at half the dose that studies over up to 5 years found no evidence of it. It does not apply to people taking vitamin B6 as medical treatment, who should be under a doctor's care. The European Food Safety Authority set a much lower limit in 2023 — see Where official guidance disagrees, below.

What it does

Vitamin B6 is the name for six related compounds, including pyridoxine; their active coenzyme forms are pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate ^[1]. It takes part in more than 100 enzyme reactions, mostly in protein metabolism, and is also involved in the metabolism of carbohydrates and fats ^[1]. It helps make neurotransmitters, keeps blood homocysteine at normal levels, and is involved in making glucose, immune function and forming hemoglobin ^[1].

Forms

The most common form in supplements is pyridoxine hydrochloride, although some contain PLP ^[1]. Absorption from supplements is similar to absorption from food and does not differ much between forms; the body absorbs large doses well but quickly excretes most of the excess in urine ^[1]. About 28% to 36% of people take a supplement containing vitamin B6 ^[1].

Where it comes from

Chickpeas, canned1 cup1.1 mg
Beef liver, pan fried3 ounces0.9 mg
Tuna, yellowfin, fresh, cooked3 ounces0.9 mg
Salmon, sockeye, cooked3 ounces0.6 mg
Chicken breast, roasted3 ounces0.5 mg

How these five were chosen: The five foods with the most vitamin B6 per serving in the NIH fact sheet's food table. Fortified foods are marked.

How far one serving goes toward a day's vitamin B6

How far one serving goes toward a day's vitamin B6
Item	Percent of the adult daily amount (1.3 mg)
Chickpeas	85%
Beef liver	69%
Tuna, yellowfin	69%
Salmon (sockeye)	46%
Chicken breast	38%

Against the recommended daily amount for adults 19 to 50: 1.3 mg. Where a food varies by brand, the bar shows the lowest figure and the label the full range. Computed from the figures on this page, taken from the NIH fact sheet.

Getting the most from it

About 75% of the vitamin B6 in a mixed diet is available to the body ^[1]. Much of the pyridoxine naturally present in fruits, vegetables and grains is in forms that are less available ^[1].

In the United States

Most Americans get the recommended amount: average intake is about 2 mg a day for men and 1.5 mg for women ^[1]. Even so, in 2003–2004 data, 24% of people who did not take a supplement containing vitamin B6, and 11% of those who did, had low blood PLP (below 20 nmol/L) — some even at intakes of 2.0 to 2.9 mg a day, above the recommended amount ^[1]. Levels were lower in women than men, in non-Hispanic black than non-Hispanic white people, in current smokers and in people who were underweight; the authors concluded that the recommended amounts might not guarantee adequate status in many groups ^[1].

Who is most likely to run low

People with poor kidney function, including those on dialysis or who have had a kidney transplant ^[1]
People with autoimmune disorders, including rheumatoid arthritis, celiac disease and inflammatory bowel disease ^[1]
People with alcohol dependence, in whom blood PLP tends to be very low ^[1]

What deficiency looks like

Isolated deficiency is uncommon; low vitamin B6 usually comes with low levels of other B vitamins, such as vitamin B12 and folic acid ^[1]. Deficiency is associated with microcytic anemia, abnormal brain-wave recordings, dermatitis with scaling on the lips and cracks at the corners of the mouth, a swollen tongue, depression and confusion, and weakened immune function ^[1]. People with borderline status or mild deficiency might have no signs for months or even years ^[1]. Kidney disease, malabsorption syndromes such as celiac disease, Crohn's disease and ulcerative colitis, some genetic diseases and some medicines, such as antiepileptic drugs, can cause deficiency ^[1].

What the evidence supports, and what it doesn't

Established. Vitamin B6 is needed for more than 100 enzyme reactions, and too little causes anemia, skin and mouth changes, depression and confusion ^[1]. The recommended amounts were calculated to keep blood PLP at 20 nmol/L or more ^[1].

Not supported by trials. Heart disease: B vitamins lower homocysteine, but most large trials have not found that they reduce cardiovascular events ^[1]. In a combined analysis of two Norwegian trials in 6,837 patients with ischemic heart disease, 40 mg of vitamin B6 a day, with or without folic acid and vitamin B12, had no benefit on major cardiovascular events ^[1]. Cancer: the same Norwegian trials found no link between vitamin B6 supplements and cancer or deaths ^[1]. Cognition: a systematic review of 14 trials found insufficient evidence that vitamin B6, alone or with vitamin B12 or folic acid, affects cognitive function ^[1].

Mixed. Premenstrual syndrome: a meta-analysis of nine trials in almost 1,000 women found vitamin B6 more effective than placebo, but most studies were small and several had weaknesses; in a later trial in 94 women, 80 mg a day over three cycles reduced a broad range of symptoms ^[1]. Nausea in pregnancy: two trials found that 30 to 75 mg a day reduced nausea, but a Cochrane review could not draw firm conclusions; vitamin B6 combined with the antihistamine doxylamine reduced nausea and vomiting by 70% in trials ^[1]. The American College of Obstetricians and Gynecologists recommends vitamin B6 as a first treatment, and the fact sheet advises pregnant women to consult a physician first, because the doses could approach the upper limit ^[1].

Where official guidance disagrees

In 2023, the European Food Safety Authority set an upper limit for vitamin B6 of 12 mg a day for all adults, including women who are pregnant or breastfeeding, based on systematic reviews of vitamin B6 and nerve damage ^[1]. That is about an eighth of the U.S. limit of 100 mg ^[1].

Too much

Vitamin B6 from food has not been reported to cause harm ^[1]. Taking 1 to 6 g of pyridoxine a day for 12 to 40 months can cause severe, progressive sensory neuropathy — nerve damage with loss of control of body movements — which usually stops if the supplements are stopped as soon as symptoms appear ^[1]. Several reports describe neuropathy at doses below 500 mg a day ^[1]. Excess vitamin B6 can also cause painful, disfiguring skin lesions, sensitivity to light, nausea and heartburn ^[1].

Medicines that interact

Cycloserine (Seromycin), an antibiotic used for tuberculosis, increases the loss of vitamin B6 in urine, which might worsen the drug's seizures and nerve toxicity; vitamin B6 supplements can help prevent this ^[1]. Antiepileptic drugs such as valproic acid, carbamazepine and phenytoin lower blood PLP and raise homocysteine, and 200 mg a day of pyridoxine can lower blood levels of phenytoin and phenobarbital ^[1]. Theophylline, used for asthma and other lung diseases, is often accompanied by low blood PLP, which could contribute to its side effects, including seizures ^[1]. If you take any of these regularly, talk to your doctor or pharmacist before taking a vitamin B6 supplement.