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Pyridoxal 5'-phosphate (PLP) in serum/plasma

Published: August 9, 2026Updated: August 16, 2026

This test measures the active form of vitamin B6 (pyridoxal 5'-phosphate) in your blood. Vitamin B6 is essential for many body functions, including nerve function, metabolism, and red blood cell production.

Quick summary

["Assessing your vitamin B6 status through its active form can help identify deficiencies or excesses that may affect health."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
75043-0
Short code
Vit B6 CSF-sCnc
Synonyms
Vit B6 CSF-sCnc
Category
chemistry
Sample
csf
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
1-2 mL
Stability
Immediate analysis required, Refrigerated: 1h
Hemolysis max
200
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms like fatigue, nerve pain, or unusual cravings for non-food items. It may also be used to monitor vitamin B6 levels in people with certain medical conditions, such as anemia, epilepsy, or kidney disease.

What to Expect During the Test

A small blood sample will be taken from a vein in your arm. You may feel a slight pinch, but it usually doesn’t cause significant discomfort. The sample is then sent to a lab for analysis.

What the Results Mean

Results help determine if your body has enough active vitamin B6 to function properly. Low levels might indicate a deficiency, while very high levels could suggest overconsumption or certain medical conditions.

Common Reasons for Testing

Doctors often check vitamin B6 levels when diagnosing or managing conditions linked to metabolism, nerve health, or red blood cell production. It’s also used in research or to assess dietary needs.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Vitamin B6 Metabolite

Frequently asked questions

How might my vitamin B6 levels affect my health?
Low levels of pyridoxal 5'-phosphate can lead to deficiencies that may cause neurological issues, anemia, or weakened immune function. High levels might require medical evaluation to rule out conditions like alcoholism or certain medications.
What should I do if my results are outside the normal range?
If your results are low, your doctor may recommend dietary changes, supplements, or further testing to identify the cause. If high, they may investigate potential causes like medications or underlying health issues.
Does diet affect this test?
Yes, vitamin B6 is found in foods like chicken, potatoes, and fortified cereals. Avoiding excessive supplements or certain medications (like anticonvulsants) for a few days before testing may help provide more accurate results.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy