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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, which is essential for many metabolic processes and nerve function.

Quick summary

["PLP helps your body process amino acids and supports 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
2900-9
Short code
Vit B6 SerPl-mCnc
Synonyms
Vit B6 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, or if you have conditions like anemia, epilepsy, or certain genetic disorders. It may also be checked in people with malabsorption issues or those taking medications that deplete vitamin B6.

What to Expect Before the Test

No special preparation is needed, but you may be asked to fast for a few hours before the blood draw. Wear a comfortable shirt for easy access to your arm.

What the Results Mean

Results help assess whether your body has enough vitamin B6 to function properly. Very low levels may suggest dietary deficiencies or medical conditions affecting absorption.

Common Conditions Linked to PLP Levels

Low PLP levels can be linked to vitamin B6 deficiency, which may cause neurological symptoms, while high levels might indicate overconsumption or certain metabolic disorders.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

PLP is a critical cofactor for enzymes involved in neurotransmitter synthesis, amino acid metabolism, and hemoglobin production. Abnormal levels may signal underlying health concerns that require further evaluation, such as genetic disorders or malabsorption syndromes.

Short name

PLP Level

Frequently asked questions

What causes vitamin B6 levels to be checked?
Your doctor may order this test if you have symptoms like numbness, depression, seizures, or unusual fatigue, or if you’re taking medications that can deplete vitamin B6 (e.g., some antibiotics or anticonvulsants). It may also be part of a broader evaluation for conditions like anemia or nerve damage.
How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab’s processing time. Your provider will discuss them with you during your follow-up visit.
Can I take vitamin B6 supplements if my levels are low?
Only follow your healthcare provider’s advice—supplements should be used cautiously, as excessive intake can also cause side effects or mask underlying deficiencies in other vitamins.
  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