Vitamin B6 Side Effects: How Much Is Too Much

Vitamin B6 side effects are unusual among vitamins: the mechanism is well established, the harm is nerve damage, and the safe limit is far lower than what many supplements contain.

Vitamin B6 sits in almost every B-complex and energy supplement on the shelf, usually with no warning attached, which is how an overdose happens by accident rather than by intent. EFSA describes the relationship between excess intake and nerve damage as well established (1). The limit it set is 12 milligrams a day.

Key Takeaways

• EFSA’s upper limit for adults is 12 mg/day, based on nerve damage (1).
• The damage is sensory, not weakness — numbness, tingling, unsteadiness (2)(4).
• In 7 documented adults, 4 were severely disabled; all improved after stopping (2).
• Symptoms can keep worsening for 2 to 3 weeks after you stop (3).
• EFSA: only regular supplement users are likely to exceed the limit (1).

Vitamin B6: The Limit, And Why It Exists

In 2023 EFSA reviewed the evidence and set a tolerable upper intake level. The wording of the reasoning is unusually direct: the relationship between excess vitamin B6 intakes and the development of peripheral neuropathy is well established and is the critical effect on which the UL is based (1).

The panel identified a reference point of 50 mg/day from a case-control study, supported by case reports and vigilance data, then applied an uncertainty factor of 4 to account for the fact that the higher the dose, the faster symptoms appear (1). That produced 12.5 mg/day. A separate calculation from a dog study gave 11.7. The panel took the midpoint, rounded down, and set 12 mg/day for adults, including during pregnancy and breastfeeding (1).

And the line that explains who this article is for: EU populations are unlikely to exceed the limits except for regular users of food supplements containing high doses of vitamin B6 (1).

You will not get near this from food. You can pass it with one tablet.

Where B6 Comes From In Food

Those figures are from the USDA FoodData Central database 6, and they are the reason the limit is a supplement question rather than a diet one.

The richest ordinary food on the list is raw pistachios at 1.7 mg per 100 g. To reach the 12 mg adult limit from pistachios alone you would need to eat roughly 700 grams in a day, and that is the easiest route on the table. From chicken breast it is about two kilograms. From bananas, more than three.

Compare that with a single high-strength B-complex tablet carrying 50 or 100 mg, and the picture resolves itself. Every case of B6 neuropathy in the literature above involved supplements or prescribed pyridoxine, not diet.

There is one middle category worth knowing about: fortified products. Breakfast cereals, energy drinks and meal-replacement shakes often have B6 added, and because it is added rather than naturally present, the amounts can be far higher than the food itself would carry. Those count towards your total in a way that a banana does not.

B6 Toxicity: What The Damage Actually Is

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A systematic review of 20 articles characterised the pattern (4). Higher B6 levels, usually occurring after taking supplements, lead to a predominantly, if not exclusively, sensory neuropathy of the axonal type (4).

The original description came in 1983, in a paper titled Sensory neuropathy from pyridoxine abuse: a new megavitamin syndrome (2). Seven adults developed ataxia and severe sensory-nervous-system dysfunction after daily high-level B6. Four were severely disabled. All improved after withdrawal (2).

Two details from that paper are worth holding onto. Weakness was not a feature, and the central nervous system was clinically spared (2). So this does not present as muscles failing. It presents as numbness, tingling, burning, and a loss of the sense of where your limbs are — which is why unsteadiness is often the first thing people notice.

The authors called for safe guidelines for this widely abused vitamin (2). That was forty years ago.

It Is A Dose Relationship, And It Has Been Tested Deliberately

One study did something that would be hard to get approved today: it gave five healthy volunteers either 1 or 3 grams of pyridoxine a day and watched for the first sign of trouble, stopping immediately when it appeared (3).

All of them became symptomatic. Those on the higher dose became symptomatic earlier (3). The authors concluded there is a clear dose relationship for pyridoxine-induced neuropathy (3).

The part that catches people out

The same study found something practically important. After pyridoxine was stopped and blood levels had returned to normal, symptoms continued to progress for two to three weeks (3).

The researchers call this coasting, and they specifically note it appeared unrelated to persistently elevated blood levels (3).

Why it matters: someone who stops the supplement and then gets worse over the following fortnight may reasonably conclude the supplement was not the problem, and go back to it.

Does It Reverse?

Usually. Not always completely.

In the 1983 series, all seven improved after withdrawal, including the four who had been severely disabled (2). The systematic review reports the same direction: patients improve after discontinuing pyridoxine (4).

But a documented case of a 54-year-old man taking 600 mg a day alongside isoniazid tells the other side. A nerve biopsy showed marked loss of large myelinated fibres. Improvement only began once pyridoxine was stopped, and a four-year follow-up found recovery very slow and still incomplete (5). The authors raised the possibility of unusual individual susceptibility (5).

Six hundred milligrams is not an extreme figure by supplement standards. That is the uncomfortable part.

And The Reverse Claim: Does B6 Treat Nerve Problems?

Not established, and the review is careful about why.

Low B6 does show up in people with peripheral neuropathy of various causes, but there is no firm evidence that low B6 levels have a direct causal relationship with it (4). Several studies report subjective improvement after B6, but no data exist on B6 as a monotherapy — only as part of combinations with other vitamins (4).

The review’s own summary: the potential therapeutic role cannot be confirmed to date, while the neurotoxic role at high levels is supported (4).

One genuinely reassuring finding sits alongside it: supplementation at permitted daily doses has not been proven harmful, even in people who already have neuropathy (4). The problem is dose, not the vitamin.

What To Do

Read the milligrams, not the name. High-strength B-complex, energy and “nerve support” formulas often carry 25, 50 or 100 mg of B6. The adult limit is 12 (1).

Add up everything you take. B6 appears in multivitamins, B-complexes and energy products at once.

Food is not the risk. EFSA’s own exposure analysis puts supplement users in the exceeding group, nobody else (1). An ordinary balanced diet does not get near it.

If you have numbness, tingling or unsteadiness and take B6, tell a doctor what dose you are on. This is diagnosable and it is reversible in most cases (2)(4).

Do not expect immediate improvement on stopping. Coasting for two to three weeks is documented (3).

For the opposite problem — a B vitamin where deficiency damages nerves — see our guide to B12 deficiency.

Frequently Asked Questions

What are the symptoms of B6 toxicity?
Sensory, and they start in the feet and hands. Numbness, tingling, burning and a loss of the sense of where your limbs are, which is why unsteadiness is often the first thing people notice. Muscle weakness is not a feature, and that is one of the distinguishing marks: in the 1983 series of seven adults the central nervous system was clinically spared and weakness was absent, yet four of them were severely disabled. A systematic review of 20 articles found the same pattern, describing a predominantly, if not exclusively, sensory neuropathy of the axonal type. An overdose of this kind comes from supplements, not from food.

How much vitamin B6 is too much?
Lower than most supplement labels suggest. In 2023 EFSA set the tolerable upper intake level for adults, including pregnant and breastfeeding women, at 12 milligrams a day. The reference point behind that figure was 50 mg a day, identified from a case-control study and supported by case reports and vigilance data, with an uncertainty factor of 4 applied. For children the limits are lower still: 3.2 to 4.5 mg a day for ages one to six, and 6.1 to 10.7 mg a day for seven to seventeen. EFSA also noted that EU populations are unlikely to exceed these limits except for regular users of supplements containing high doses.

What does vitamin B6 nerve damage feel like?
It is a sensory problem rather than a weakness problem, and that pattern is consistent across the literature. A systematic review of 20 articles found that higher B6 levels, usually from supplements, lead to a predominantly and often exclusively sensory neuropathy of the axonal type. The original 1983 case series described seven adults with ataxia, meaning unsteadiness and poor coordination, and severe sensory nervous system dysfunction. Weakness was specifically not a feature and the central nervous system was clinically spared. Numbness, tingling, burning and unsteadiness are the typical picture.

Does it get better if I stop?
Usually, but not always quickly and not always completely. In the 1983 series all seven patients improved after withdrawal, even though four had been severely disabled. The systematic review reports that patients subjectively improve after stopping pyridoxine. But one documented case of a man taking 600 mg a day showed a four-year follow-up with very slow and still incomplete recovery, and the authors raised the possibility of unusual individual susceptibility to pyridoxine toxicity. Stopping is the treatment; a full return to normal is likely but not guaranteed.

Why did my symptoms get worse after I stopped?
This has a name and it is documented. In a prospective study, five healthy volunteers were given either 1 or 3 grams of pyridoxine a day and were taken off it at the first sign of any abnormality. Symptoms continued to progress for two to three weeks after stopping, despite blood levels of pyridoxal phosphate returning to normal. The researchers called this coasting, and noted it appeared unrelated to blood levels of the toxin still being high. It matters practically because someone who stops and then feels worse may wrongly conclude the supplement was not the cause.

Can vitamin B6 treat neuropathy?
This is where the marketing and the evidence part company, and it is worth separating the two directions. Low B6 levels are seen in people with peripheral neuropathy of various causes, but the systematic review found no firm evidence that low B6 has a direct causal relationship with it. Several studies report subjective improvement after B6 supplementation, but no data exist on B6 given as a monotherapy, only as part of combination treatments with other vitamins. The review concluded that a therapeutic role for B6 cannot be confirmed. Meanwhile the neurotoxic role at high levels is described as well established.

Is it dangerous to take a B-complex supplement?
Not at normal doses, and the review is reassuring on this specific point: supplementation with vitamin B6, even as part of a multivitamin, has not been proven harmful at permitted daily doses, including in people who already have neuropathy. The issue is products carrying doses well above the 12 mg adult limit, which are common in high-strength B-complex and energy formulas. Check the actual milligram figure on the label rather than assuming that a vitamin sold freely must be within safe limits.

The Bottom Line

Vitamin B6 is a rare case where a freely sold vitamin has a well-established mechanism of harm and a limit most people have never heard of. EFSA set the adult tolerable upper intake at 12 mg a day, with peripheral neuropathy as the critical effect, and noted that only regular supplement users are likely to exceed it. The damage is sensory rather than muscular: numbness, tingling and unsteadiness, described in 1983 in seven adults of whom four were severely disabled, all of whom improved after stopping. A prospective study showed a clear dose relationship, with every volunteer on 1 to 3 grams a day becoming symptomatic, and symptoms continuing to worsen for two to three weeks after withdrawal. Recovery is usual but not guaranteed: one case at 600 mg a day was still incomplete four years later.

This article is for informational purposes only and is not a substitute for professional medical advice. Do not stop prescribed vitamin B6, which is sometimes given deliberately alongside medicines such as isoniazid, without speaking to your doctor. See a doctor about new numbness, tingling, burning or unsteadiness, and tell them every supplement and dose you take.

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