Vitamin B6 Toxicity: Can It Cause Nerve Damage?

Key Takeaways

• Excess vitamin B6, primarily from supplements, can cause peripheral neuropathy.
• Vitamin B6 toxicity is less from foods and more from supplements.
• Many supplements contain vitamin B6, including many multivitamins and magnesium supplements.
• Tingling and burning and numbness in the hands and feet and disturbances of balance may be early signs of the condition.
• Early recognition and avoidance of high doses may help prevent progression of damage to the sensory nerves.

What Is Vitamin B6 Toxicity?

Although vitamin B6 is an essential nutrient, too much vitamin B6 from supplements can be toxic. Toxicity is due to the high levels of vitamin B6 causing damage to the sensory nerves. The U.S. NIH states that the repeated high doses of vitamin B6 supplements can lead to irreversible nerve damage.

It is usually easy to obtain an adequate amount of vitamin B6 by consuming a varied diet. Sources of vitamin B6 include fish and poultry, potatoes and bananas, and fortified cereals and cereal products, and legumes.

Can Vitamin B6 Supplements Cause Nerve Damage?

• Vitamin B6 supplements can damage nerves. Excessive vitamin B6 can cause peripheral neuropathy.
• Peripheral neuropathy can lead to tingling, numbness, pain and loss of balance. High supplemental doses of vitamin B6 can damage sensory nerves. The exact reason is unclear.
• However, there are many published clinical cases and safety evaluations that report high doses of vitamin B6 and tingling and numbness.
• Reports to the Therapeutic Goods Administration (TGA) from 2021 and 2022 detail adverse effects of vitamin B6 containing products including neuropathy.
• Of the 32 cases where the TGA determined a possible cause was related to the product, 21 cases used 50mg of vitamin B6 daily, and 9 cases used multiple vitamin B6 containing products.
• The TGA reports do not indicate how often cases of vitamin B6 toxicity occur, but demonstrate the importance of addressing combination product use.

Symptoms of Vitamin B6 Toxicity

The symptoms of B6 toxicity develop gradually and can be attributed to other conditions, so B6 toxicity is often unreported. Common symptoms include:

• Pins and needles
• Burning extremities
• Numbness
• Impaired balance
• Position Sense

Vitamin B6 can also cause nausea, heartburn, skin reactions, increased sensitivity to the sun, and nerve weakness. Continued nerve weakness can also be caused by a number of other conditions including diabetes and certain medications.

How Much Vitamin B6 Is Too Much?

The amount of vitamin B6 that can cause nerve related side effects varies between individuals. There are a number of factors that impact risk including total intake of B6 from other supplements, the dose, and duration of use. There is not a set safe dose to ensure that adverse effects will not occur.

The following table shows adult recommendations and safety limits.

The U.S. upper limit was set by the NIH, Office of Dietary Supplements, and the EFSA upper limit was set in 2023. These differing opinions and upper limits do not mean either is the recommended supplemental dose.

It is also important to note that the U.S. upper limit of 100 mg does not mean 100 mg is the true upper limit. There are adverse effects of vitamin B6 at doses lower than 100 mg, and there are unsafe effects of taking multiple supplements containing B6.

Which Supplements May Contain Too Much Vitamin B6?

Vitamin B6 toxicity can be found in supplements that are labelled as vitamin B6 supplements and in many other products. These include:

• Multivitamin and mineral supplements
• Vitamin B-complex supplements
• Some magnesium supplements
• Some zinc supplements
• Some products marketed for ‘energy’ and general ‘wellness’

Check the ingredient list for names like pyridoxine hydrochloride, pyridoxal 5′-phosphate (P-5-P), and pyridoxal 5′-phosphate monohydrate.

People could unknowingly consume too much vitamin B6 from supplements they are taking for other reasons, and the TGA cautions about this. Adding the amounts from each label together could show you if you are taking too much.

How Is Vitamin B6 Toxicity Diagnosed?

Depending on your symptoms and history, your health care professional may order blood tests to check the levels of vitamin B6.

Although neuropathy is a symptom of vitamin B6 toxicity, it can also be caused by many other conditions. Hence your health care professional may test for conditions like diabetes, B12 deficiency, and others. Depending on your symptoms your health care professional may also order other tests or refer you to a neurologist.

You should carry your supplement bottles or a picture of their labels to your appointment. This helps your health care professional know about the supplements you are taking and identify other supplements that may also be causing your problems. Your health care professional may also help determine your total daily intake of B6.

How Is Vitamin B6 Toxicity Treated?

The first, and most important, step in managing confirmed vitamin B6 toxicity is cessation of the vitamin B6 supplements, if any, under appropriate medical oversight. There is no specific antidote for pyridoxine toxicity.

Recovery varies. Some improve after the source is removed. Improvement may take months, and nerve damage may not fully recover in some cases. Continuing exposure after symptom development is of concern for progression.

New tingling, burning, or numbness with a vitamin B6-containing product warrants stopping the suspected product and contacting a healthcare professional as soon as possible. If vitamin B6 is being prescribed or taken to address a medical condition, contact the prescriber before adjusting the treatment.

How Can You Prevent Vitamin B6 Toxicity?

A few things can help avoid excessive intake:

• Don’t take more than one supplement at a time that contains vitamin B6 unless told to do so by a doctor or health care professional.
• Don’t assume that a supplement is safe to take in high doses just because it is available without a prescription.
• Only take a supplement for the reason for which it is given and take it according to the directions.
• If you have nerve symptoms, see a doctor.

Conclusion

Vitamin B6 is an essential vitamin for health, but too much of the vitamin can potentially damage nerves and cause neuropathy. Vitamin B6 toxicity can be found in different types of supplements including multivitamins, and products containing magnesium.

It is important to recognize symptoms of peripheral neuropathy and contact a healthcare professional for an evaluation. It is important to use vitamin supplements responsibly, and not take too many supplements that contain vitamin B6.