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Urine Ornithine-to-Creatinine Ratio

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

Measures urinary ornithine relative to creatinine. It may be used in evaluating suspected amino acid metabolism disorders, including homocystinuria.

Quick summary

["This urine test helps assess how much ornithine is being excreted relative to creatinine."]

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

Key facts at a glance

LOINC
22682-9
Short code
Ornithine/Creat Ur-sRto
Synonyms
Ornithine/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 the amount of ornithine in urine compared with the amount of creatinine. Creatinine is used to account for urine concentration, so the ratio can help show how much ornithine is being excreted.

Why might I need this test?

This test may be used when evaluating an infant or child with signs of a possible inherited amino acid metabolism disorder. It is often associated with screening or follow-up for homocystinuria, in which abnormal homocysteine metabolism can affect the eyes, bones, clotting, and nervous system.

How is the test performed?

A urine sample is tested in a laboratory, and the amount of ornithine is compared with the amount of creatinine in the same sample. The laboratory may use a specialized analytical method to measure the substances.

How do I prepare for the test?

Follow the laboratory's instructions for urine collection type and timing. Collection method can matter for this test, so ask whether a first-morning, random, or timed urine sample is required and whether any dietary restrictions apply.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine ornithine-to-creatinine ratio

Frequently asked questions

Is this the same as a blood ornithine test?
No. This test measures ornithine in urine relative to creatinine. A blood ornithine measurement is a separate test and may be used to clarify the diagnosis.
What does the creatinine part of the result mean?
Creatinine is a waste product used to help adjust the ornithine measurement for urine concentration. The ratio is more useful than the raw urine ornithine value alone, particularly when urine is dilute or concentrated.
Does one abnormal result confirm a metabolic disorder?
No. An abnormal result may suggest a problem but can also reflect other factors. A clinician will interpret it with symptoms, age, family history, and confirmatory laboratory testing.
  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