Which B vitamin can cause nerve damage? A guide to B6 toxicity and B12 deficiency

October 22, 2025 •

3 min read

According to reports by the Therapeutic Goods Administration (TGA), cases of peripheral neuropathy suspected to be related to vitamin B6 are on the rise, highlighting the risk from excessive supplementation. This makes it more important than ever to understand which B vitamin can cause nerve damage, and to distinguish between toxicity from overdose and deficiency from insufficient intake.

Quick Summary

Certain B vitamins can cause nerve damage under specific conditions. Excess vitamin B6 from supplements leads to toxicity, while a deficiency in vitamin B12 can also impair nerve function.

Key Points

B6 Toxicity: Excessive intake of vitamin B6, typically from high-dose supplements, is a known cause of peripheral nerve damage.
B12 Deficiency: A lack of vitamin B12 can also cause neuropathy by damaging the protective myelin sheath surrounding nerves.
Supplement Caution: Toxicity from vitamin B6 is almost always linked to supplement use, not dietary intake, and can occur from taking multiple products containing the vitamin.
Watch for Symptoms: B6 toxicity symptoms include numbness, tingling, and poor balance, while B12 deficiency can cause similar sensations plus cognitive issues.
Doctor's Guidance: It is critical to consult a healthcare provider before taking high-dose B vitamin supplements to prevent toxicity or properly treat a diagnosed deficiency.
Reversibility: Some nerve damage from both B6 excess and B12 deficiency may be permanent, especially if severe or prolonged, although symptoms can often improve after treatment.

The Two Sides of the B Vitamin Coin

While all B vitamins are essential for bodily functions, their relationship with nerve health is complex. Nerve damage can result from both an overconsumption of one B vitamin and a lack of another. The most common B vitamins involved in nerve damage are excessive intake of vitamin B6 and a severe deficiency of vitamin B12.

Vitamin B6 Toxicity: When Too Much is a Bad Thing

Unlike most other water-soluble B vitamins, high doses of vitamin B6 (pyridoxine) can be toxic to the nervous system, leading to peripheral neuropathy. This nerve damage occurs when excess B6 from supplements interferes with nerve function and is not typically associated with B6 from food.

Symptoms of B6 Toxicity

Numbness and tingling, often in the hands and feet.
Painful sensations.
Difficulty walking and maintaining balance.
Loss of muscle control.
Muscle weakness.
Reduced sensation to pain or temperature.

How Much B6 is Too Much?

B6 toxicity usually occurs with supplement doses significantly exceeding the recommended daily intake. The US tolerable upper intake level for adults is 100 mg per day. However, some individuals have reported neuropathy at lower doses over time. Taking multiple supplements containing B6, such as a multivitamin and a B-complex, can lead to excessive intake.

Vitamin B12 Deficiency: The Damage from a Lack of Nutrients

A deficiency in vitamin B12 (cobalamin) is another known cause of nerve damage. B12 is vital for maintaining the myelin sheath that protects nerves. A lack of B12 can cause this protective layer to break down, impairing nerve function.

Causes of B12 Deficiency

Pernicious anemia.
Vegan or vegetarian diets.
Malabsorption issues from conditions like Crohn's disease or gastric bypass surgery.
Certain medications.
Decreased absorption with age.

Symptoms of B12 Deficiency Neuropathy

Pins and needles sensation.
Balance problems and loss of coordination.
Memory loss and confusion.
Muscle weakness.

Comparison of Nerve Damage: B6 Toxicity vs. B12 Deficiency


Feature	Vitamin B6 Toxicity	Vitamin B12 Deficiency
Cause	Excessive intake, primarily from high-dose supplements.	Inadequate intake, malabsorption issues, or medication effects.
Mechanism	Interference with nerve function, possibly involving neurotransmitters and direct nerve damage.	Breakdown of the myelin sheath.
Symptoms	Numbness, tingling, burning pain, and difficulty with balance.	Numbness, tingling, balance problems, vision issues, and cognitive impairment.
Recovery	Symptoms may improve after stopping supplements, but recovery can be slow and damage may be permanent.	Treatment can stop progression and sometimes improve symptoms, but severe, long-term damage may be irreversible.
Prevention	Monitoring total B6 intake from all supplements and avoiding high doses.	Ensuring adequate dietary intake, especially for those at risk, and using supplements as advised by a healthcare provider.

Making Smart Dietary Choices

A balanced diet is the safest way to meet B vitamin requirements. Most individuals can get enough B vitamins from food without high-dose supplements.

For Vitamin B6: Good sources include poultry, fish, potatoes, chickpeas, bananas, and fortified cereals.
For Vitamin B12: Found in animal products like meat, fish, eggs, and dairy. Vegans may need fortified foods or supplements.

Consult a healthcare professional before starting any new supplements, especially if you have existing health conditions or take multiple products. A proper nutrition diet should focus on whole foods and address deficiencies under medical guidance.

Conclusion: Navigating B Vitamins for Nerve Health

Understanding the risks of both excessive vitamin B6 from supplements and a deficiency in vitamin B12 is vital for preventing nerve damage. Prioritizing a balanced diet, being aware of total B6 intake, and seeking professional advice for potential deficiencies are key steps in protecting your nervous system. For further details on nutritional neuropathies, resources such as the National Institutes of Health provide valuable information.

Frequently Asked Questions

No, it is extremely rare to get toxic levels of vitamin B6 from food alone. B6 toxicity is almost always caused by consuming high doses of the vitamin through supplements over an extended period.

Diagnosis typically involves a blood test to measure vitamin B12 levels. Further tests might be needed to determine the underlying cause, such as checking for intrinsic factor antibodies in cases of suspected pernicious anemia.

Early signs of B6 toxicity often include numbness and tingling, frequently beginning in the hands and feet. Some people may also experience a burning sensation or difficulty with balance.

If caught and treated early, nerve damage from a B12 deficiency is often reversible. However, if the deficiency is severe and has persisted for a long time, some neurological damage may be permanent.

B12 injections are used for people who have malabsorption issues, such as those with pernicious anemia or who have undergone gastric surgery, and cannot absorb the vitamin from oral supplements effectively.

The US tolerable upper intake level (UL) for adults is 100 mg of vitamin B6 per day from supplements. However, as documented by regulatory agencies, adverse effects have been reported at lower dosages for some individuals, so caution is advised.

While B6 toxicity and B12 deficiency are the primary causes of B vitamin-related neuropathy, other deficiencies like thiamine (B1) can also lead to nerve damage, though this is rare in developed countries.