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Vitamins & Minerals

Vitamin B6 (Pyridoxine)

Vitamin B6 is a vitamin your body needs for energy, healthy nerves and making red blood cells. Unusually, both too little and too much can harm the nerves — and high levels almost always come from supplements, not food. The blood test measures the active form your cells use, so it can flag either a shortfall or a build-up.

Targeted Testing
CategoryVitamins & Minerals
Reference rangeSee your report
Evidence○Targeted Testing
Last updated3 July 2026
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What is vitamin b6 (pyridoxine)?

Vitamin B6 helps your body use and store energy from the protein and carbohydrates in food. It also helps make haemoglobin — the protein inside red blood cells that carries oxygen around your body. The biologically active form of vitamin B6 is pyridoxal-5-phosphate (PLP) — a coenzyme that sits inside enzymes and enables many chemical reactions throughout the body. When a lab measures your B6, it is usually measuring PLP directly. What makes B6 unusual among vitamins is that both ends of the spectrum carry risk. Too little can lead to deficiency symptoms affecting the blood, skin and nervous system. But too much — almost always from high-dose supplements rather than food — can accumulate in the blood and damage nerves, causing peripheral neuropathy (tingling, numbness or pain in the hands and feet). This means the test is used to look in both directions.

Why is it tested?

A vitamin B6 test is ordered when deficiency is suspected — for example, in someone with unexplained anaemia, a rash, mood changes, or nerve symptoms — or when a high level is suspected in someone taking B6 supplements. It may also be checked as part of a broader B-vitamin workup alongside B12 and folate. Certain medications, including isoniazid (used to treat tuberculosis) and levodopa (used in Parkinson's disease), can affect B6 metabolism and may prompt testing if you take them.

Reference range (Australia)

Use the reference interval printed on your report — vitamin B6 is measured as PLP (its active form), and both low and very high levels can matter nmol/L

There is no separate male/female reference interval for plasma PLP (vitamin B6). The reference interval varies by the method used and the laboratory; always use the interval printed on your own report. Both ends of the range carry clinical significance — low levels can reflect deficiency and high levels can reflect supplement accumulation.

Reference intervals vary between laboratories. Always use the range printed on your own report.

What your result means

If your level is low

A lower-than-range B6 level can cause a range of symptoms. Deficiency has been associated with anaemia (low red blood cell counts), a rash, seizures, and depression and confusion. Nerve-related symptoms can also appear with very low B6. Your GP will look at your result alongside your symptoms, your diet, and any medications you take that are known to affect B6 metabolism.

If your level is in range

A B6 result within range is generally reassuring. Because both deficiency and excess can affect the nerves, a result in range means neither concern applies on the current measurement. Your GP will read it in context with your symptoms and the rest of your results.

If your level is high

A higher-than-range B6 level almost always reflects supplement use. When too much vitamin B6 builds up in the body, it can accumulate in the blood and damage nerves — a condition called peripheral neuropathy (tingling, numbness or pain, usually in the hands and feet). Importantly, eating vitamin B6 from food, even in large amounts, does not cause toxicity. The concern is with high-dose supplements taken over time. If your B6 is elevated and you take a B6 supplement, that is worth mentioning to your GP at your next visit — they can advise whether the dose and duration are appropriate.

What can affect your result

Diet contributes B6, but food sources almost never cause a high result — even large dietary amounts do not accumulate to toxic levels. The main driver of high B6 is supplements, particularly at doses above the recommended upper limit. Alcohol use and chronic gut conditions (such as coeliac disease or inflammatory bowel disease) can impair B6 absorption and push levels down. Certain medications — including isoniazid (a tuberculosis antibiotic) and levodopa (a Parkinson's medication) — can also affect how the body handles B6. Inflammation can lower PLP levels independently of actual intake, so a slightly low result in someone who is unwell may partly reflect that rather than true dietary deficiency. Pregnancy increases B6 requirements and can lead to lower circulating levels.

When to act

If your B6 is low and you have symptoms — unexplained anaemia, a rash, mood or nerve changes — that is worth a conversation with your GP. They will consider your diet, medications and circumstances. If your B6 is high and you take a B6 supplement, it is worth mentioning to your GP. The recommended upper limit for vitamin B6 is 50 milligrams per day, and supplements often contain far more than this. A high B6 from supplements is something your GP can advise on, and worth raising with them before any nerve symptoms appear. This page is general information and is not a substitute for advice from your GP.

Frequently asked questions

Vitamin B6 helps your body use and store energy from protein and carbohydrates in food. It also helps make haemoglobin — the protein inside red blood cells that carries oxygen around your body. And it is an essential vitamin that helps your nervous system function. The active form in your cells is pyridoxal-5-phosphate (PLP), which acts as a helper molecule (coenzyme) in a large number of enzyme reactions throughout the body.

Yes, and this is an important point. When too much vitamin B6 builds up in the body — almost always from supplements rather than food — it can accumulate in the blood and damage nerves, causing peripheral neuropathy (tingling, numbness or pain, typically in the hands and feet). The recommended upper limit is 50 milligrams per day. Eating vitamin B6 from food, even in large amounts, does not cause toxicity — it is a supplement issue rather than a dietary one.

Vitamin B6 deficiency has been associated with anaemia (a drop in healthy red blood cells), a rash, seizures, and depression and confusion. Nerve symptoms can also appear at very low levels. Because these symptoms overlap with other conditions, the blood test helps your GP confirm whether B6 is part of the picture — it is read alongside your symptoms and other results rather than in isolation.

PLP stands for pyridoxal-5-phosphate, and it is the biologically active form of vitamin B6 — the version that is actually used inside your cells to drive enzyme reactions. The lab measures PLP specifically because it reflects how much active B6 is available to your body, rather than just how much total B6 is circulating. This gives a more meaningful picture of your functional B6 status.

No. Eating vitamin B6 from food, even in large amounts, does not cause toxicity, poisoning or overdose. The concern with too much B6 is specific to high-dose supplements — not to dietary sources like chicken, fish, bananas or fortified cereals. If you are eating a varied diet and not taking B6 supplements, a high B6 result from food alone is not expected.

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