Vitamin B6 Nerve Damage From High Doses

Vitamin B6 is a water-soluble nutrient most people get easily from food, and high intakes from food alone have not been reported to cause harm. However, long-term high-dose supplementation is linked to sensory neuropathy, a form of nerve damage that can affect how you feel touch, pain, and temperature.

What Vitamin B6 Does in the Body

According to the NIH Office of Dietary Supplements (ODS), vitamin B6 acts as a coenzyme in more than 100 enzyme reactions, most of them involved in protein and amino acid metabolism. The evidence for this role is graded as strong. The nutrient also supports the metabolism of one-carbon units, carbohydrates, and lipids, and it contributes to cognitive development through the biosynthesis of neurotransmitters.

One well-supported function is helping maintain normal blood homocysteine levels, which the NIH ODS also rates as strong evidence. Other proposed benefits, including reducing cardiovascular disease risk, preventing cancer, or improving cognitive function in older adults, are currently rated as insufficient evidence by the NIH ODS. Evidence that vitamin B6 may help relieve nausea and vomiting in pregnancy is rated as moderate, and evidence for reducing premenstrual syndrome symptoms is rated as limited.

Supplements are not intended to diagnose, treat, cure, or prevent any disease, and these statements have not been evaluated by the FDA.

How Much Vitamin B6 Do Adults Need?

The NIH ODS reports the following reference values for adults aged 19 to 50 years:

• Recommended Dietary Allowance (RDA): 1.3 mg per day for both men and women
• Tolerable Upper Intake Level (UL): 100 mg per day for all adults aged 19 and older

The UL applies to combined intake from food and supplements. Most people who eat a varied diet reach the RDA without supplementation. Over-the-counter B6 supplements often contain doses that are many times higher than the RDA, so it is worth checking labels carefully.

The European Safety Authority Sets a Lower Limit

In 2023, the European Food Safety Authority (EFSA) set a notably lower upper limit of 12 mg per day for all adults, including during pregnancy and lactation. This figure is substantially below the 100 mg per day UL set by the U.S. Food and Nutrition Board (FNB). The gap between these two limits reflects ongoing scientific discussion about where the threshold for harm actually lies. If you are in Europe or simply want to apply a more conservative standard, the EFSA figure is worth knowing.

What Is Sensory Neuropathy?

Sensory neuropathy means damage to the sensory nerves, the nerves that carry signals about touch, temperature, vibration, and pain from the body to the brain. When vitamin B6 is taken in large amounts over a long period, it can act as a neurotoxin rather than a nutrient. The NIH ODS states clearly that long-term high-dose supplementation can cause this type of nerve damage.

Symptoms associated with supplement-induced sensory neuropathy can include:

• Numbness or tingling in the hands and feet
• Difficulty with balance or coordination
• Reduced ability to sense vibration or touch
• Pain or a burning sensation in the limbs

Symptoms often improve after stopping high-dose supplementation, but recovery can be slow and is not always complete. If you experience any of these symptoms, stop taking high-dose B6 and speak with a doctor promptly.

Why the Gap Between the RDA and the UL Matters

The RDA of 1.3 mg and the UL of 100 mg are both population reference values, not personal prescriptions. The RDA represents the amount sufficient to meet the needs of most healthy adults. The UL represents the highest daily intake that is unlikely to cause adverse effects in the general population. Regularly taking supplements that push intake close to or above 100 mg per day, especially for months or years, is where risk increases. Some single-ingredient B6 supplements and many high-potency B-complex products contain 50 mg, 100 mg, or even more per serving.

Drug Interactions to Know About

The NIH ODS identifies several important interactions between vitamin B6 and medications. Always talk to a doctor or pharmacist before combining vitamin B6 supplements with any prescription drug.

• Cycloserine (Seromycin): This antibiotic used for tuberculosis increases urinary excretion of pyridoxine and can worsen seizures and neurotoxicity. Pyridoxine supplements may help counter these effects, but only under medical supervision.
• Antiepileptic drugs including valproic acid, carbamazepine, and phenytoin: These medications increase the breakdown of vitamin B6 vitamers, lowering plasma levels of the active form and raising homocysteine. Separately, pyridoxine supplementation at 200 mg per day has been shown to reduce serum concentrations of phenytoin and phenobarbital, possibly by speeding their metabolism, which could affect seizure control.
• Levetiracetam (Keppra): Preliminary evidence suggests vitamin B6 at 50 to 100 mg per day in adults may reduce behavioral side effects such as irritability, agitation, and depression, but this evidence is still early stage.

These interactions illustrate why vitamin B6 supplementation is not a straightforward decision for people on certain medications. Consult a clinician or pharmacist for guidance specific to your situation.

Practical Takeaways

• The NIH ODS adult RDA for vitamin B6 is 1.3 mg per day for adults aged 19 to 50.
• The U.S. Tolerable Upper Intake Level is 100 mg per day; the 2023 EFSA limit is 12 mg per day.
• High intakes from food have not been linked to harm, but long-term high-dose supplements can cause sensory neuropathy.
• Check supplement labels, since many B-complex and standalone B6 products contain doses well above the RDA.
• Nerve damage symptoms such as tingling, numbness, or balance problems warrant prompt medical attention.
• Talk to a doctor before taking B6 supplements if you use antiepileptic drugs, cycloserine, or any other prescription medication.

Sources

All nutrient data in this guide is drawn from the NIH Office of Dietary Supplements Vitamin B6 fact sheets and the National Academies Dietary Reference Intakes report for B vitamins. For full references, see the NIH ODS health professional fact sheet at ods.od.nih.gov and the National Academies Press catalog entry for Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline.