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Urine Ornithine-to-Creatinine Ratio

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

A urine test that compares the amount of ornithine with creatinine, helping account for differences in urine concentration.

Quick summary

["This ratio can help identify conditions in which unusually high amounts of ornithine are released in the urine."]

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

Key facts at a glance

LOINC
13786-9
Short code
Ornithine/Creat Ur
Synonyms
Ornithine/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 ornithine, an amino acid involved in protein metabolism and the urea cycle, relative to creatinine in a urine sample. Creatinine is used as a reference to help account for how concentrated or dilute the urine is.

Why might I need this test?

The test may be used to evaluate suspected disorders of amino acid metabolism, including primary hyperornithinemia and certain urea-cycle disorders. It may be ordered alongside urine amino acid testing and other genetic or metabolic studies.

How is the test performed?

You provide a urine sample according to your clinician's instructions. The laboratory measures ornithine and creatinine in the sample and calculates their ratio.

How do I prepare for the test?

Follow the urine-collection instructions exactly, as this may be a first-morning, random, or timed collection. Tell your clinician about supplements, medicines, pregnancy, or any recent illness that could affect the result.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

An elevated urine ornithine-to-creatinine ratio may indicate increased urinary excretion of ornithine, as can occur in primary hyperornithinemia and some urea-cycle disorders. The result must be interpreted with the absolute urine amino acid levels, symptoms, medical history, and other tests because urine concentration, age, medications, and diet can affect the ratio.

Short name

Urine ornithine/creatinine ratio

Frequently asked questions

Is this the same as a serum amino acid test?
No. This test evaluates ornithine relative to creatinine in urine, while a serum amino acid test measures amino acids in blood. Your clinician may order both to help evaluate a suspected metabolic disorder.
Does the test require fasting?
Fasting is not usually required for a urine ornithine-to-creatinine ratio, but the collection method and preparation should follow your clinician's instructions. A first-morning or timed urine sample may be requested.
What does an elevated ratio mean?
It can indicate that more ornithine than expected is being excreted in urine. Possible causes include inherited metabolic conditions, so the result is generally reviewed together with other laboratory and 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