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Pyridoxal (PDL) to Creatinine Ratio, Urine

Published: August 9, 2026Updated: August 16, 2026

Measures urinary pyridoxal relative to creatinine, helping assess vitamin B6 excretion while accounting for urine concentration.

Quick summary

["This urine ratio can help evaluate vitamin B6 status and identify unusually high or low pyridoxal excretion."]

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

Key facts at a glance

LOINC
81798-1
Short code
PDL/Creat Ur-sRto
Synonyms
PDL/Creat Ur-sRto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

What is this test?

This test measures pyridoxal, a form of vitamin B6, in urine and compares it with the amount of creatinine in the same sample. The ratio helps account for differences in urine concentration.

Why might I need this test?

It may be ordered to evaluate vitamin B6 metabolism or status, particularly when dietary intake, supplement use, or symptoms suggest an abnormality. Your clinician will interpret it alongside your medical history and other tests.

How is the test performed?

A urine specimen is collected according to your clinician's instructions. The laboratory measures pyridoxal and creatinine and calculates the pyridoxal-to-creatinine ratio.

How do I prepare for the test?

No special preparation is usually required unless your clinician provides specific collection instructions. Tell the healthcare team if you take vitamin B6 supplements or a multivitamin, because supplements can affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urinary pyridoxal-to-creatinine ratio

Frequently asked questions

What does the pyridoxal-to-creatinine ratio measure?
It compares the amount of urinary pyridoxal with urinary creatinine. Creatinine is included as a reference for how concentrated the urine sample is.
Do I need to stop taking vitamin B6 supplements before this test?
Do not stop supplements unless your clinician instructs you to do so. Instead, report the dose and timing of any vitamin B6 or multivitamin supplements so the result can be interpreted appropriately.
Does an abnormal result diagnose a vitamin B6 disorder by itself?
No. Results are interpreted with symptoms, diet, supplement use, kidney function, and other vitamin B6 tests when available.
  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