BiomarkersVitamin B6 (PLP)

Vitamins

Vitamin B6 (PLP)

For brain chemicals and homocysteine clearance

On your report it may say: Pyridoxal 5-phosphate, PLP, Pyridoxine

This test measures PLP, the active form of vitamin B6. B6 helps make brain chemicals like serotonin and helps clear homocysteine. Both low and high levels can affect nerves.

Updated 2026-10-26

Typical ranges · µg/L

Low below 5
In range 5–50
High 50+

nmol/L = µg/L × 4.05

High results are common in people taking B6 or B-complex supplements.

Ranges vary by lab, age and sex. The range printed on your report applies.

If it's low

B6 may be too low for normal nerve and brain chemical function.

Common causes

  • Heavy alcohol use
  • Kidney disease
  • Some medicines (isoniazid, certain anti-seizure drugs)
  • Autoimmune conditions

What you might notice

  • Cracks at the corners of the mouth
  • Low mood or irritability
  • Tingling

If it's high

High B6 almost always comes from supplements. Long-term high intake can cause nerve damage.

Common causes

  • B6 or B-complex supplements
  • Energy drinks with added B vitamins

What you might notice

  • Numbness or tingling in hands and feet
  • Poor balance

Testing

Who should test
Anyone taking B6 supplements with tingling, or with signs of deficiency.
How to prepare
Fasting is usually required; stop B6 supplements 24 hours before.
When to retest
3 months after a change.

What can help

Food sources

BananasChickpeasPotatoesPoultry and fishNuts

See a doctor if you have numbness or tingling, especially while taking B6.

Common questions

Can too much B6 hurt?

Yes. Long-term high doses can damage nerves; that's the main reason to check.

Is B6 in my multivitamin?

Usually, so add up all sources.

Explore further

When to take them

Sources

  1. NIH Office of Dietary Supplements: Vitamin B6 fact sheet for health professionals

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For general education only, not medical advice. Ranges shown are typical for adults; the range printed on your lab report applies. Talk to a qualified doctor about your results.