Vitamin B6 (Pyridoxal 5-Phosphate) Measurement
This test measures the amount of vitamin B6 in your body, usually by checking the level of its active form, pyridoxal 5-phosphate (PLP), in your blood. It helps your care team see whether you have too little or too much vitamin B6.
["A vitamin B6 test helps identify a deficiency or excess of this essential nutrient, which can cause nerve and blood problems when levels are abnormal."]
Key facts at a glance
- LOINC
- 47203-5
- Short code
- Vit B6 Dose
- Synonyms
- Vit B6 Dose
- 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
What Vitamin B6 Does
Vitamin B6, also called pyridoxine, is a water-soluble vitamin your body needs for many everyday functions. It helps process proteins and carbohydrates, supports red blood cell formation, and plays a role in normal nerve and brain function. Because your body does not store much of it, you need a steady supply from food.
Why Your Provider May Order It
Your healthcare provider may order this test if you have symptoms that could point to low or high vitamin B6, such as numbness or tingling in the hands and feet, unusual fatigue, or certain types of anemia. It may also be checked if you take vitamin B6 supplements, have a condition that affects nutrient absorption, or use medicines that can change vitamin B6 levels.
How the Sample Is Collected
The test is usually done on a blood sample drawn from a vein in your arm. In some cases, your provider may ask for a urine sample instead. Preparation instructions vary, so follow any directions you are given about fasting or holding supplements before the test.
Understanding Your Results
Results are generally interpreted as low, normal, or high compared with the laboratory's own range. A low level can suggest a deficiency, while a high level may reflect supplement use or another cause. Because reference ranges differ between laboratories and the testing method matters, ask your provider to explain what your specific result means for you.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Vitamin B6 is important for nerve function and red blood cell production, so levels that are too low or too high can cause meaningful symptoms. Deficiency may lead to skin changes, anemia, or nerve problems, while excessive intake—often from high-dose supplements—can also cause nerve damage. Test results are always interpreted alongside your symptoms, diet, supplement use, and other laboratory findings, and they help guide whether treatment or changes to supplementation are needed.
Short name
Vitamin B6
Frequently asked questions
Do I need to fast or stop taking vitamins before this test?
Can taking vitamin B6 supplements affect my result?
What happens if my vitamin B6 level is abnormal?
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