Australia will significantly tighten the regulation of dietary supplements with vitamin B6 (pyridoxine) starting in 2027, under a reclassification by the Therapeutic Goods Administration. Products with more than 50 mg of vitamin B6 will then be available only in pharmacies, and those with more than 200 mg will require a prescription. The move follows numerous reports of sometimes severe sensorimotor polyneuropathies after long-term high-dose supplementation.

Concerns are also growing in Germany that B6 supplements are underestimated. “A restriction of over-the-counter [OTC] availability would be desirable here as well,” said Hans-Jürgen Gdynia, chief of neurology at m&i Fachklinik Enzensberg, a specialist clinic and rehabilitation center located in Füssen, Germany. Preparations with B vitamins are “advertised in pharmacies, on television, and online as beneficial for the nerves.” The problem, he said, is that many people “equate over-the-counter with harmless.” That belief is deceptive.

The German Federal Institute for Risk Assessment (BfR) has recommended since last year that adults and adolescents aged 15 years or older should not consume more than 0.9 mg of vitamin B6 per day from supplements. The European Food Safety Authority (EFSA) in 2023 lowered the tolerable total daily intake for adults from 25 mg/d to 12 mg/d. Amounts above that are considered unsafe. For children, upper limits range from 2 mg/d to 11 mg/d depending on body weight.

High-Dose Products Still Sold OTC

Despite these very low recommendations, the German market still offers numerous products with 25-50 mg of vitamin B6 per capsule or tablet, both as single-ingredient products and as part of high-dose B-complex vitamins. Investigation of supplements for toddlers and preschoolers, as well as earlier analysis of sports supplements sold online, shows that some products contain vitamin B6 levels that exceed age-appropriate reference values or the presumed safe upper limits many times over.

How many people actually take such products long-term is unknown. Studies usually assess overall supplement use rather than targeted B6 supplementation. Clinicians observe, however, that many patients combine multiple products and thereby unknowingly reach high total doses.

B6-Associated Polyneuropathies

That high B6 intake can be neurotoxic has been known for decades. As early as 1983, a team in The New England Journal of Medicine reported sensory neuropathy from chronic high-dose pyridoxine use, with symptoms often improving after the supplement was stopped.

What is new is how often such cases now occur. At this year’s German Society for Neurology congress, Gdynia and colleagues presented a case series of eight patients who developed polyneuropathy due to B6 hypervitaminosis. “And these are only patients who presented to our neurology clinic over 4 years,” he emphasized. “So it’s not as rare as you think.”

The affected individuals had taken OTC products — mostly B-complex vitamins, often for “general strengthening,” in some cases on a physician’s recommendation. “Extremely high-dose preparations aren’t even necessary. The hypervitaminosis in all cases arose from products bought at a pharmacy or drugstore,” Gdynia said.

Include B6 in Routine Workup

Given this clustering, Gdynia calls for changes in diagnostic practice. “In polyneuropathy, you should always check the B6 level,” he said. Many cases are overlooked because histories do not specifically ask about supplements, and B6 is often not measured in unclear neuropathies.

In his view, this diagnostic gap should be reflected in the guideline “Diagnostics in polyneuropathies” of the German Society for Neurology, which currently recommends measuring vitamin B6 only in certain cases, not generally. “This belongs in routine diagnostics,” he emphasized. The reason: B6-induced neuropathy is potentially reversible. “After stopping the preparation, many cases improve gradually, provided the damage has not lasted too long.”

Moderate Long-Term Doses Can Harm

In Australia, approximately 250 cases of B6-induced polyneuropathy were reported before the regulatory decision. The majority involved people who had taken 100-200 mg/d or more over extended periods.

At very high doses, a polyneuropathy can occur in about 1%-4% of those chronically exposed, still rare but by no means negligible, said Peter Crack, a neuropharmacologist at The University of Melbourne, Melbourne, Australia, in comments to the Australian Science Media Centre. “Even moderate but sustained intakes (eg, 50 mg/d over months to years) have been linked to sensory neuropathy in susceptible individuals.”

“Neuropathy is rarely seen with dietary intake alone and occurs almost exclusively in people taking supplements at doses well above physiological needs,” Crack emphasized.

Water-Soluble Vitamin Myth

It is widely believed that water-soluble vitamins are harmless because excess amounts are excreted. “I also learned in medical school that only fat-soluble vitamins are stored and can be dangerous,” Gdynia said. “But too much vitamin B6 can obviously cause significant harm in the body.”

Awareness of hypervitaminosis is “not sufficiently developed in either the general population or the medical community.” Patients rarely volunteer information about self-purchased supplements, and physicians often do not specifically ask about supplements in the workup of polyneuropathies.

Stricter Rules Needed

Following the new EFSA assessment, the BfR proposed in 2024 that supplements for adults contain no more than 0.9 mg of vitamin B6 per daily dose. Even stricter limits apply for children. However, these values are not legally binding. That explains why products with 20-50 times higher contents are still available in drugstores and online shops.

Gdynia, therefore, advocates for clearer regulation, similar to that in Australia. “The dangers posed by hypervitaminosis are not sufficiently highlighted. We need more education and stricter rules.”