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Phenyl Lactate-to-Creatinine Ratio, 24-Hour Urine

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

Measures urinary phenyl lactate relative to creatinine in a 24-hour urine collection, helping account for differences in urine concentration.

Quick summary

["This test measures phenyl lactate excretion and is primarily used in the evaluation of disorders of phenylalanine metabolism."]

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

Key facts at a glance

LOINC
50359-9
Short code
Phenyllactate/Creat 24h Ur-sRto
Synonyms
Phenyllactate/Creat 24h Ur-sRto
Category
kidney
Sample
urine
Container
Sterile urine container
Units
N/A
Critical range
— – 4 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 phenyl lactate in urine and compares it with the amount of creatinine in the same 24-hour collection. Creatinine is used as a marker of urine concentration so the phenyl lactate result is less affected by variations in urine volume.

Why might I need this test?

The test may be used when evaluating or monitoring a condition involving phenylalanine metabolism, such as phenylketonuria. Results are best interpreted alongside dietary intake, medications, age, and other clinical findings.

How is the test performed?

You collect all urine for exactly 24 hours into a container provided by the laboratory or healthcare professional. The laboratory then measures phenyl lactate and creatinine and may calculate their ratio.

How do I prepare for the test?

Follow the collection instructions provided by your healthcare professional, including the exact start and stop times. Keep the container closed, refrigerate it if instructed, and document any urine that was missed during the collection period.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

An elevated phenyl lactate-to-creatinine ratio may indicate increased urinary phenyl lactate, which can occur with abnormal phenylalanine metabolism, including inadequately controlled phenylketonuria. Results can also be affected by diet, medications, urine collection problems, and changes in creatinine excretion, so they should be interpreted by the treating clinician.

Short name

Urine phenyl lactate ratio

Frequently asked questions

Why is urine collected for 24 hours?
A 24-hour collection provides a more complete estimate of substances excreted in the urine than a single specimen. The result is also adjusted using creatinine to account for urine concentration.
Do I need to fast for this test?
Fasting is generally not required unless your healthcare professional gives specific instructions. Maintain your usual diet and medication routine unless you are told otherwise, because these can affect the result.
What happens if part of the urine collection is missed?
A missed collection can make the 24-hour result less accurate. Contact the laboratory or healthcare professional for guidance on whether the collection needs to be repeated.
  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