Platform
Company
Urinalysis
Review status
Currently under review
Pending specialist review and validation.
This test measures the amount of leucine, an essential branched-chain amino acid, in your urine. Because urine can be more or less concentrated, the result is typically reported relative to creatinine to make results easier to compare across different samples.
Leucine is important for protein building and energy use. Measuring it in urine helps clinicians evaluate how your body processes amino acids. It is often ordered together with other branched-chain amino acids, such as isoleucine and valine, as part of a targeted metabolic workup.
Urine leucine can help identify problems with amino acid metabolism or kidney reabsorption, and it is useful in evaluating or monitoring inherited metabolic conditions that affect branched-chain amino acids. It can also reflect nutritional management in people who require specialized diets or medical formulas.
Your clinician may order this test if a newborn screen is abnormal, if there are symptoms concerning for a metabolic disorder, or to monitor a known condition over time. The test uses a urine sample and has minimal risk, but interpretation always considers your age, diet, hydration, overall health, and results of related tests.
A higher urine leucine result can occur with increased dietary intake, illness-related tissue breakdown, or an inherited condition that affects how your body uses branched-chain amino acids. Dehydration can make urine appear more concentrated, while excess fluid intake can dilute it, which is why results are adjusted to creatinine. Your care team will interpret the value alongside other amino acids, your symptoms, and clinical history.
A lower result is usually not concerning by itself. If you are being treated for a metabolic disorder, your team may focus on patterns over time rather than a single value. Depending on your situation, follow-up may include plasma amino acids, a full urine amino acid profile, genetic testing, or nutrition adjustments. If you feel unwell or have new symptoms, contact your clinician for personalized guidance.
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.
High-protein meals, medical formulas, or branched-chain amino acid supplements can raise urine leucine. Tell your clinician about sports supplements, special formulas, or recent dietary changes.
Fever, infections, injury, or surgery increase protein breakdown and can elevate urine leucine. Testing when you are well versus ill may yield different results.
Very concentrated or very dilute urine can affect results. Reporting relative to creatinine helps, but providing a typical midstream sample and avoiding extreme fluid intake before collection can improve consistency.
Corticosteroids, certain hormones, and total parenteral or enteral nutrition can alter amino acid levels. Share your medication list and any tube feeding or specialized nutrition with the lab and clinician.
Infants and young children can normally excrete different amounts of amino acids than older children and adults. Age-specific reference intervals are used for interpretation.
Conditions that affect kidney tubules, such as generalized aminoaciduria or tubular dysfunction, can increase urinary amino acids. Your clinician may review kidney tests if results are unexpected.
References