Vitamin B6

What it actually measures

Vitamin B6 is a cofactor for over a hundred enzyme reactions, which is a wide remit even by vitamin standards.

It is required to build neurotransmitters including serotonin, dopamine and GABA. It is part of how your body makes haemoglobin. It is needed for amino acid metabolism, and it is one of the three cofactors that clear homocysteine, alongside B12 and folate.

It comes in three natural forms: pyridoxine, pyridoxal and pyridoxamine. Supplements most commonly use pyridoxine, and the active form in your body is pyridoxal 5-phosphate, sometimes sold as P5P.

Deficiency is genuinely uncommon on a reasonable diet, since it is widespread in food.

So on paper this is an unremarkable water-soluble vitamin, and water-soluble usually means excess simply gets excreted.

That assumption is exactly what makes B6 worth a page, because it is the exception.

The direction nobody expects

A 2023 systematic review in Nutrients set out to characterise vitamin B6-related peripheral neuropathy, searching PubMed and including 20 articles.

Its conclusion on the excess side is direct. Higher vitamin B6 levels, which usually occur following the taking of nutritional supplements, may lead to the development of a predominantly, if not exclusively, sensory neuropathy of the axonal type.

Sensory means the symptoms are numbness, tingling, burning and altered sensation, typically starting in the feet and hands, rather than weakness.

The review also reported that after pyridoxine discontinuation, such patients subjectively report improved symptoms, which is encouraging and not the same as saying it always fully resolves.

It stated plainly that current scientific evidence supports a neurotoxic role of B6 at high levels.

Now the deficiency side, handled with the same care. The review found that while low B6 levels are seen in people with peripheral neuropathy of various causes, there is no firm evidence that low B6 has a direct causal relationship with it.

And on treatment, it noted that many studies suggest subjective improvement in neuropathy symptoms after B6 supplementation, but no data exist on B6 as a monotherapy, only as part of combination treatment usually with other vitamins. So the therapeutic role cannot be confirmed.

The review was also careful to say that supplementation at permitted daily doses has not been proven harmful in patients who already have neuropathy.

That is an unusually clean summary: the harm from excess is supported, the benefit from correction is not established, and the symptom picture is the same in both directions.

What moves it

Down: genuinely uncommon on a reasonable diet. Contributors include heavy alcohol intake, which impairs metabolism of B6, kidney disease and dialysis, some medications including isoniazid and certain others, coeliac disease and other malabsorption, and pregnancy through increased demand.

Up: supplements, which is the route that matters. B6 appears in multivitamins, B complexes, energy formulas, magnesium products and premenstrual blends, frequently at doses many times the requirement. High-dose B6 is also used therapeutically in some conditions, which is a prescriber decision rather than a shelf decision.

The honest hedge

I am not a doctor and I am not diagnosing anyone.

The single most useful thing on this page is that the symptoms of too much and too little look similar. Numbness and tingling in the hands and feet can point either way, which means guessing is a genuinely bad idea here in a way it is not for most vitamins.

If you have those symptoms and you take supplements, add up your total B6 before you add any more. That is the specific mistake worth avoiding.

I would also not want this read as a reason to fear B6 in food or in a sensible multivitamin. The review explicitly noted that supplementation at permitted daily doses has not been proven harmful even in people who already have neuropathy.

The concern is high-dose, sustained, and usually accidental, arising from taking several products that each contain B6 without adding them up.

Do not stop a prescribed high-dose B6 regimen on your own, since it is used deliberately in some conditions. That is a prescriber conversation.

And new or worsening numbness, tingling or balance problems belong with a doctor regardless of what your supplements contain, because the differential is long and some of it is time-sensitive.

So. What to actually do.

Tonight, at no cost. Read every label and add up your total B6 in milligrams. It hides in multivitamins, B complexes, magnesium blends, energy formulas and premenstrual products, and people routinely take three things containing it.

Compare that total to the requirement. Adult requirements sit in the low single-digit milligrams. Many supplements contain tens or hundreds.

If you have numbness or tingling and take B6, do not add more. The symptoms of excess and shortfall overlap, which is exactly why guessing is a poor idea here.

Take new neurological symptoms to a doctor. That is true regardless of your supplements, and mention what you take, because B6 excess is easy to miss if nobody says.

If you want the functional picture, test the pathway. Homocysteine reflects whether B6, B12 and folate together are doing their job, alongside a B12 and folate panel.

Do not stop a prescribed regimen yourself. High-dose B6 is used deliberately in some conditions.

Prefer food and modest doses. B6 is widespread in food and deficiency is uncommon on a reasonable diet.

You are not short of everything. Sometimes you are carrying too much of something you never chose deliberately, spread across three bottles nobody added up.

Your body is not broken. It is blocked. And with this one, the block can come from either direction, which is the whole reason to count rather than guess.

Go read your labels and add up the milligrams.