Urine Tyrosine

The Urine Tyrosine test measures the amount of tyrosine, an amino acid, excreted in your urine. Tyrosine comes from dietary protein and normal protein turnover in the body, and it is used to make important compounds such as neurotransmitters and hormones. Many laboratories report tyrosine relative to creatinine to account for how concentrated or dilute the urine is.

This test is often used in infants and children when doctors are evaluating amino acid metabolism or checking for certain inherited metabolic conditions. It may also be used to monitor nutrition or treatment plans, and it is frequently ordered together with plasma amino acids and other metabolic markers.

Abnormal urinary tyrosine can suggest problems in how the body breaks down tyrosine, including inherited conditions known as tyrosinemias. It can also reflect secondary issues such as immature liver function in newborns, liver disease, or changes related to diet or illness. Identifying these patterns helps clinicians decide if further evaluation or treatment is needed.

Your clinician may order this test after an abnormal newborn screen, when there are symptoms such as poor growth or liver concerns, or to monitor medication such as nitisinone. Results help distinguish temporary, nutrition-related changes from conditions that require targeted therapy and long-term follow-up.

Your result is interpreted in the context of your age, symptoms, and other tests. Because the value is often adjusted for urine concentration, it is compared with expected values for your age group. Small shifts can occur with what you eat, hydration, or minor illnesses and do not always indicate a medical problem.

Higher values can occur with certain inherited enzyme deficiencies, prematurity, liver stress, or high protein intake. Lower values are usually not concerning. If your result is outside the expected range, your clinician may repeat the test or order additional studies, such as plasma amino acids, succinylacetone testing, liver enzyme tests, or genetic testing, to clarify the cause and guide next steps.