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Vitamin B6 (Pyridoxine) Metabolite – Pyridoxal 5'-Phosphate (PLP) in Serum

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

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

Quick summary

["PLP helps your body use protein, convert food into energy, and maintain healthy nerves—low levels may signal vitamin B6 deficiency."]

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

Key facts at a glance

LOINC
75041-4
Short code
Pyridoxal SerPl-sCnc
Synonyms
Pyridoxal SerPl-sCnc
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
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-nutritious foods. It could also be part of a broader evaluation for vitamin deficiencies, anemia, or certain neurological conditions.

What to Expect Before the Test

No special preparation is usually needed. You may fast for 8–12 hours before the test if instructed, but always follow your provider’s directions. Bring any medications you’re taking, as some may affect results.

What the Results Mean

Results help determine if your body is getting enough vitamin B6. While reference ranges vary by lab, very low levels may indicate poor absorption or dietary insufficiency, while very high levels could suggest certain medications or metabolic conditions.

Common Conditions Linked to PLP Levels

Low PLP is often associated with vitamin B6 deficiency, which can cause neurological issues, anemia, or weakened immune function. High levels may be linked to conditions like liver disease or certain medications.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

PLP (Serum)

Frequently asked questions

What causes vitamin B6 deficiency?
Deficiency can result from poor diet (low intake of foods like poultry, fish, or fortified grains), malabsorption issues (e.g., celiac disease), or certain medications (e.g., anticonvulsants). Chronic alcohol use or pregnancy may also contribute.
How long does it take to see results?
Test results are typically available within 1–3 business days, depending on your lab. Follow-up with your provider to discuss interpretation and next steps.
Can I adjust my diet before testing?
Avoid making drastic dietary changes. If you suspect a deficiency, discuss dietary adjustments with your provider before testing to avoid misleading 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