Pyridoxal 5'-phosphate (PLP) concentration in serum/plasma
This test measures the active form of vitamin B6 (pyridoxal 5'-phosphate) in your blood. Vitamin B6 is essential for many bodily functions, including metabolism and nerve health.
["PLP helps support energy production and nerve function; low levels may indicate vitamin B6 deficiency."]
Key facts at a glance
- LOINC
- 26915-9
- Short code
- Vit B6 Bld Ql
- Synonyms
- Vit B6 Bld Ql
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
What Is Pyridoxal 5'-phosphate (PLP)?
Pyridoxal 5'-phosphate (PLP) is the biologically active form of vitamin B6, a water-soluble vitamin that plays a key role in metabolism, red blood cell production, and nerve function. Your body converts dietary vitamin B6 into PLP for use in enzymes that help break down proteins, fats, and carbohydrates. It also supports the production of neurotransmitters like serotonin and dopamine, which are important for mood and brain function.
Why Might You Need This Test?
Doctors may order a PLP test if you have symptoms of vitamin B6 deficiency, such as fatigue, nerve pain, or unusual skin changes. It may also be used in research or clinical settings to assess vitamin B6 status in patients with certain metabolic disorders, neurological conditions, or those on specific diets.
How Is the Test Performed?
A blood sample is drawn from a vein, usually in your arm. The sample is sent to a lab where PLP levels are measured using an immunoassay method, which detects the presence of PLP in your serum or plasma.
What Do the Results Mean?
Results are typically reported as a concentration value (e.g., micrograms per deciliter). While reference ranges can vary by lab, low PLP levels may suggest vitamin B6 deficiency, while very high levels could indicate certain metabolic conditions or medication use. Your doctor will interpret results in the context of your overall health and symptoms.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low PLP levels may indicate inadequate vitamin B6 intake or absorption, which can lead to deficiencies affecting metabolism, nerve function, or red blood cell production. Conversely, excessively high levels may rarely be associated with metabolic disorders or certain medications. Monitoring PLP is particularly important for individuals with conditions like hemolytic anemia, epilepsy, or those on long-term vitamin B6 supplements.
Short name
PLP Blood Test
Frequently asked questions
What causes low PLP levels?
What are the symptoms of vitamin B6 deficiency?
How can I prevent vitamin B6 deficiency?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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