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Phenylalanine/Creatinine Ratio, 24-Hour Urine

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

This test measures urinary phenylalanine relative to creatinine over 24 hours. It can help assess phenylalanine excretion while accounting for differences in urine concentration.

Quick summary

["The result helps evaluate how much phenylalanine is being lost in urine, which is especially useful in monitoring phenylketonuria."]

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

Key facts at a glance

LOINC
44348-1
Short code
Phe/Creat 24h Ur
Synonyms
Phe/Creat 24h 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 24-hour urine test measures the amount of phenylalanine in the urine and compares it with the amount of creatinine. Creatinine is used as a reference because urine volume and concentration can vary from day to day.

Why might I need this test?

This test may be used to monitor people with phenylketonuria, an inherited condition in which the body does not process phenylalanine normally. It can also help evaluate dietary phenylalanine intake and the effectiveness of treatment.

How is the test performed?

You collect all urine for 24 hours in a labeled container provided by the laboratory. The laboratory measures phenylalanine and creatinine and calculates their ratio.

How do I prepare for the test?

Follow the laboratory's collection instructions carefully and record the start and finish times. Keep the container refrigerated if instructed, return the full collection within the specified time, and tell the care team about medicines, supplements, and major dietary changes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

24-Hour Urine Phenylalanine/Creatinine Ratio

Frequently asked questions

Why is creatinine included in this test?
Creatinine helps account for how concentrated the urine is. Using a ratio can make the phenylalanine result more meaningful than a urine concentration alone.
How do I collect a 24-hour urine sample?
Collect all urine during the full 24-hour period using the provided container, including urine produced at the end of the collection period. Follow the laboratory's instructions for storage, timing, and delivery.
Does this test replace blood phenylalanine monitoring?
No. It provides information about urinary phenylalanine excretion and may support treatment monitoring, but it is interpreted alongside blood tests and other clinical findings.
  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