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Urine Xanthurenine-to-Creatinine Ratio

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

This urine test measures xanthurenine relative to creatinine to help evaluate vitamin B6 metabolism and investigate certain metabolic or neurologic symptoms.

Quick summary

["The result can provide information about vitamin B6 metabolism, but it must be interpreted alongside symptoms, medications, and other tests."]

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

Key facts at a glance

LOINC
101990-0
Short code
Xanthuren/Creat Ur
Synonyms
Xanthuren/Creat Ur
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 the amount of xanthurenine, a substance formed during vitamin B6 metabolism, relative to the amount of creatinine in urine. Creatinine is used to account for differences in urine concentration.

Why might I need this test?

It may be ordered when a clinician is evaluating vitamin B6 metabolism or unexplained neurologic, developmental, or metabolic symptoms. It may also help assess how medications or supplements that affect vitamin B6 are influencing the body.

How is the test performed?

A urine sample is collected and analyzed in the laboratory. The laboratory measures xanthurenine and creatinine and calculates their ratio.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional, including whether a first-morning, timed, or 24-hour urine sample is required. Tell the clinician about vitamin B6 supplements and medications; do not stop prescribed treatment unless instructed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Xanthurenine/Creatinine Ratio

Frequently asked questions

What does the xanthurenine-to-creatinine ratio measure?
It measures the relative amount of xanthurenine to creatinine in urine. Creatinine helps adjust the result for variations in urine concentration.
What conditions can affect this result?
Vitamin B6 deficiency or impaired metabolism, certain medications, and kidney function can influence the result. The laboratory and your clinician will interpret it in context.
Do I need to stop taking supplements before the test?
Do not stop supplements or medications without medical advice. Tell your clinician about all supplements, especially vitamin B6 products, because they may affect the result.
  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