Skip to content

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 important for nerve function, red blood cell production, and metabolism.

Quick summary

["PLP helps support energy metabolism and nerve health; low levels may indicate vitamin B6 deficiency."]

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

Key facts at a glance

LOINC
26057-0
Short code
Vit B6 p Vit B6 PO SerPl-mCnc
Synonyms
Vit B6 p Vit B6 PO SerPl-mCnc
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 nerve pain, fatigue, or unusual mood changes. It could also be part of a broader evaluation for vitamin deficiencies, metabolic disorders, or conditions affecting red blood cells.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for 8–12 hours before the draw if your lab uses a specific protocol. Wear a comfortable shirt for easy access to your vein.

What the Results Mean

Results help determine if your body has enough vitamin B6 to function properly. Very low levels may suggest dietary deficiencies or certain medical conditions, while very high levels could indicate over-supplementation or specific metabolic issues.

Common Conditions Linked to PLP Levels

Low PLP levels may be associated with nerve disorders (e.g., peripheral neuropathy), anemia, or conditions like sickle cell disease. High levels might raise concerns about vitamin B6 toxicity or certain genetic disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical significance: PLP is the metabolically active form of vitamin B6. It plays a critical role in neurotransmitter synthesis, hemoglobin production, and amino acid metabolism. Abnormal levels may indicate underlying deficiencies, metabolic imbalances, or conditions requiring dietary or medical intervention.

Short name

PLP Level

Frequently asked questions

What causes low PLP levels?
Low PLP levels can result from poor diet (low vitamin B6 intake), certain medications (e.g., anticonvulsants), malabsorption issues, or chronic illnesses like kidney disease or liver disorders.
What symptoms might low PLP levels cause?
Symptoms of low PLP may include tingling/numbness in hands/feet, fatigue, depression, confusion, or unusual skin rashes. Symptoms of high PLP are less common but could include nerve irritation or digestive upset.
How is PLP tested?
PLP is measured in serum or plasma using a specialized immunoassay or enzymatic method. Blood is drawn from a vein, typically in the arm, and sent to a lab for analysis.
  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