Sign in →

Test ID B6PRO Vitamin B6 Profile (Pyridoxal 5-Phosphate and Pyridoxic Acid), Plasma

Useful For

Determining the overall success of a vitamin B6 supplementation program


Diagnosis and evaluation of hypophosphatasia

Profile Information

Test ID Reporting Name Available Separately Always Performed
PLP Pyridoxal 5-Phosphate (PLP), P Yes Yes
B6PA Pyridoxic Acid (PA), P No Yes

Method Name

Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Vitamin B6 Profile (PLP and PA), P

Specimen Type

Plasma Heparin

Shipping Instructions

Ship specimen in amber vial to protect from light.

Specimen Required

Patient Preparation:

1. Fasting-overnight (12-14 hours) (infants-collect specimen prior to next feeding). Water can be taken as needed.

2. For 24 hours prior to specimen collection, patient must not take multivitamins or vitamin supplements.

Supplies: Amber Frosted Tube, 5 mL (T915)

Collection Container/Tube: Green top (sodium or lithium heparin) or plasma gel separator (PST)

Submission Container/Tube: Amber vial

Specimen Volume: 1 mL

Collection Instructions:

1. Centrifuge at 4° C within 2 hours of collection.

2. Aliquot all plasma into amber vial and freeze immediately.

Specimen Minimum Volume

0.75 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma Heparin Frozen 29 days LIGHT PROTECTED

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Clinical Information

Vitamin B6 is a complex of 6 vitamers: pyridoxal, pyridoxol, pyridoxamine, and their 5'-phosphate esters. Due to its role as a cofactor in many enzymatic reactions, pyridoxal 5-phosphate (PLP) has been determined to be the biologically active form of vitamin B6.


Vitamin B6 deficiency is a potential cause of burning mouth syndrome and a possible potentiating factor for carpal tunnel and tarsal tunnel syndromes. Persons who present with chronic, progressive nerve compression disorders may be deficient in vitamin B6 and should be evaluated. Vitamin B6 deficiency is associated with symptoms of scaling of the skin, severe gingivitis, irritability, weakness, depression, dizziness, peripheral neuropathy, and seizures. In the pediatric population, deficiencies have been characterized by diarrhea, anemia, and seizures.


Markedly elevated PLP in conjunction with low levels of pyridoxic acid are observed in cases of hypophosphatasia, a disorder characterized by low levels of alkaline phosphatase and a range of skeletal abnormalities.

Reference Values


5-50 mcg/L



3-30 mcg/L


Levels for fasting individuals falling in the range of 3 to 30 mcg/L for pyridoxic acid (PA) and 5 to 50 mcg/L for pyridoxal 5-phosphate (PLP) are indicative of adequate nutrition.


The following are interpretative guidelines based on PLP and PA results:

If PLP is >100 mcg/L and PA is ≤30:

-The increased PLP is suggestive of hypophosphatasia. Consider analysis of serum alkaline phosphatase isoenzymes (ALKI / Alkaline Phosphatase, Total and Isoenzymes, Serum) and urinary phosphoethanolamine (AAPD / Amino Acids, Quantitative, Random, Urine)


If PLP is >100 mcg/L and PA is 31 to 100 mcg/L or PLP is 81 to 100 mcg/L and PA is ≤30 mcg/L:

-The increased PLP is likely related to dietary supplementation; however, a mild expression of hypophosphatasia cannot be excluded. Consider analysis of serum alkaline phosphatase isoenzymes (ALKI / Alkaline Phosphatase, Total and Isoenzymes, Serum) and urinary phosphoethanolamine (AAPD / Amino Acids, Quantitative, Random, Urine).


If PLP is 51 to 80 mcg/L or PLP is 81 to 100 mcg/L and PA is >30 or PLP is >100 mcg/L and PA is >100 mcg/L:

-The elevated PLP is likely due to dietary supplementation.

Clinical Reference

1. Kimura M, Kanehira K, Yokoi K: Highly sensitive and simple liquid chromatographic determination in plasma of B6 vitamins, especially pyridoxal 5'-phosphate. J Chromatogr A. 1996 Jan;722(1-2):296-301. doi: 10.1016/0021-9673(95)00354-1

2. Ball GFM, ed: Vitamins: Their Role in the Human Body. Blackwell Publishing; 2004:310-325

3. Mackey AD, Davis SR, Gregory JF III: Vitamin B6. In: Shils ME, Shike M, Ross AC, et al. eds. Modern Nutrition in Health and Disease. 10th ed. Lippincott Williams and Wilkins; 2006:452-461

4. Roberts NB. Taylor A. Sodi R: Vitamins and trace elements. In: Rifai N, Horvath AR, Wittwer CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:639-718

Method Description

The stable isotope pyridoxal 5-phosphate-d2 and/or pyridoxic acid-d2 is added to plasma as an internal standard. Meta-phosphoric acid solution is then added to precipitate the proteins. Following sedimentation of the proteins, an aliquot of the clarified supernatant fluid is subjected to separation of pyridoxal 5-phosphate, pyridoxic acid, and internal standards from other plasma components by reverse-phase high-performance liquid chromatography with quantitation by tandem mass spectrometry.(Unpublished Mayo method)

Day(s) Performed

Monday through Thursday, Saturday, Sunday

Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information



LOINC Code Information

Test ID Test Order Name Order LOINC Value
B6PRO Vitamin B6 Profile (PLP and PA), P 95266-3


Result ID Test Result Name Result LOINC Value
61065 Pyridoxic Acid (PA), P 1688-1
4047 Pyridoxal 5-Phosphate (PLP), P 30552-4

Report Available

3 to 7 days


Reference ranges were established using healthy fasting volunteers who abstained from vitamin supplementation for 24 hours prior to specimen collection. Vitamin supplementation and nonfasting may result in elevated plasma vitamin concentrations.