Platform
Company
Urinalysis
Review status
Currently under review
Pending specialist review and validation.
Urine ornithine measures the amount of the amino acid ornithine that is excreted in your urine. Ornithine plays a central role in the urea cycle, the process your body uses to remove ammonia that builds up when protein is broken down. Laboratories usually report this result as a ratio to creatinine to adjust for how concentrated or dilute your urine is.
This test is often performed as part of a urine amino acids profile. It helps your care team understand how your body processes protein, how your kidneys handle amino acids, and whether a metabolic pathway may be under stress or blocked.
Abnormal urinary ornithine can suggest inherited metabolic conditions that affect the urea cycle or enzymes that use ornithine, and it may also be seen with certain liver or kidney problems. In infants and children, it can help screen for rare disorders of nitrogen handling. During treatment, it can help monitor the effects of diet or supplements that influence the urea cycle.
Your clinician may order this test if there are unexplained neurologic symptoms, vomiting, poor growth, lethargy, vision problems that raise concern for retinal disease, episodes of high ammonia, or signs of proximal kidney tubular dysfunction. Results are interpreted together with plasma amino acids, urine orotic acid, and other labs to clarify the cause and guide care.
How to interpret your result depends on your age, your overall health, and how the sample was collected. Children naturally excrete different amounts than adults, and reporting as a ratio to creatinine helps reduce the effect of hydration on the number.
Higher values can be seen with inherited metabolic disorders affecting the urea cycle, liver dysfunction, catabolic stress during illness, high protein intake, or kidney tubular problems that cause generalized aminoaciduria. Lower values may reflect low protein intake, malnutrition, or very dilute urine.
If your result is unexpected, your clinician may repeat the test, review your diet and medications, and order related studies such as plasma amino acids, urine organic acids, or genetic testing. Avoid changing your diet or supplements without medical advice, and seek prompt care if you have symptoms such as confusion, vomiting, or extreme fatigue.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Urine concentration varies with hydration and time of day. Although the result is corrected to creatinine, very dilute or very concentrated urine can still affect accuracy. First morning or properly timed collections reduce variability.
High protein meals, protein supplements, or total parenteral nutrition can increase amino acid excretion. Prolonged fasting, acute illness, or low protein intake may lower excretion or change patterns.
Arginine or citrulline supplements, corticosteroids, and valproate can influence the urea cycle and amino acid handling. Always list vitamins and over‑the‑counter products when your sample is collected.
Amino acids can degrade if the sample is left at room temperature or contaminated. Prompt refrigeration or freezing and timely transport to the lab help preserve accuracy.
Results are expressed relative to creatinine. Very low muscle mass, growth in infancy, or kidney impairment can change creatinine output and may inflate or deflate the ratio, requiring careful clinical interpretation.
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