Too much vitamin B6 can damage your nerves

High doses of vitamin B6, usually taken as pyridoxine supplements, can damage the sensory nerves, causing numbness, tingling and loss of coordination. No randomized trial has tested this; the evidence is case reports, case series, one small dosing study and national adverse-reaction reports, and it points one way. A 1983 report described seven adults who lost coordination and sensation after taking high daily doses, four of them severely disabled, and the pattern has been reported repeatedly since. The European Food Safety Authority (EFSA) based its 2023 upper limit on this effect. Most people improve after stopping, usually within six months, but some do not recover, and symptoms can keep worsening for two to three weeks after the last dose.

Where the risk begins is less settled. The clearest cases involve hundreds to thousands of milligrams a day taken for months or years. A clinical reference puts the usual threshold above 1000 mg a day, notes case reports below 500 mg a day, and says none of the studies it drew on found nerve damage below 200 mg a day. The US upper limit for adults is 100 mg a day. EFSA could not identify from human data the lowest dose that causes harm; it took 50 mg a day, from a case-control study supported by case reports and adverse-reaction data, as its starting point and set the adult upper limit, including in pregnancy and breastfeeding, at 12 mg a day. In the Netherlands, where a 2018 regulatory action set a recommended maximum of 21 mg a day for supplements, some reports of neuropathy at lower doses have continued, though reports like these cannot show how often it happens. B6 is also given as a medicine, and the US fact sheet says its upper limit does not apply to people receiving B6 as medical treatment under a physician's care.

The early case series set out the pattern. A 1985 series of 16 patients taking 0.2 to 5 g a day found a purely sensory nerve injury, and the higher the daily dose, the sooner symptoms began; every patient followed up long enough improved after stopping. In a 1992 study, five healthy volunteers were given 1 or 3 g a day; those on the higher dose developed symptoms sooner, and symptoms kept progressing for two to three weeks after stopping, even once blood levels were back to normal. The largest series, from 1987, described 172 women with raised blood B6, 60% of whom had nerve symptoms, among them tingling and numbness, that went away when B6 was stopped and came back in four women who restarted it. Those with symptoms had taken B6 for longer, 2.9 years on average against 1.6 years, though their average dose was about the same as that of the women without symptoms.

A 2023 systematic review of 20 studies concluded that higher B6 levels, usually from supplements, may lead to a mainly sensory nerve injury and that people report improvement after stopping. A 2025 analysis of 224 Dutch reports of neuropathy with B6 supplements found that after the 2018 action only one named a dose much higher than 21 mg a day, and that the dose people reported explained only 15% of the variation in their recorded blood levels.

Most reported cases involve pyridoxine, the form in most supplements. In a 24-hour laboratory study of nerve-like cells, pyridoxine killed cells while the other forms, including pyridoxal 5'-phosphate (P-5-P), did not, and pyridoxine blocked two enzymes that depend on the active form of B6. That is a cell study; none of the Sources here compares the forms in people.

UK guidance on tuberculosis gives pyridoxine alongside isoniazid in every regimen that includes it, without giving a dose or a reason on that page. The US prescribing information for pyridoxine injection lists paresthesia (tingling or numbness) among reported side effects. It advises against pyridoxine supplements for people receiving levodopa, because pyridoxine counteracts the drug, while saying it may be used with combined carbidopa and levodopa, and it describes pyridoxine as sometimes of value for nausea and vomiting in pregnancy. B6 also appears in multivitamins, B-complex and combination products, whose amounts add together. Numbness and tingling are also symptoms of nerve conditions, such as diabetic nerve damage, that B vitamins are being tested to treat. The US upper limits are lower for children, and none of the Sources here reports on nerve harm in children or in people with kidney disease. How this applies to a prescribed dose, a pregnancy or existing nerve symptoms is a conversation with the reader's clinician.

Where funding statements could be read, the money was public or none was declared: the 1983 series was funded by the US Public Health Service, the cell study by the Dutch food safety authority, and the 2023 review and the 2025 Dutch analysis declared no specific funding. For the 1985, 1987 and 1992 reports the statements could not be read.