Platform
Company
Urinalysis
Review status
Currently under review
Pending specialist review and validation.
This test measures lysine, an essential amino acid, in a urine sample. Results are typically reported relative to creatinine to account for how concentrated or dilute the urine is. This helps your care team see how much lysine your kidneys are excreting in a way that is less affected by hydration.
It is most often performed as part of a quantitative urine amino acid analysis using advanced methods such as mass spectrometry. The test is commonly used in infants and children, but it can be ordered at any age when there is concern about amino acid handling by the kidneys or certain inherited metabolic conditions.
Abnormal urinary lysine can suggest problems with how the kidney tubules reabsorb amino acids, or it can be a clue to inherited metabolic disorders that affect the transport or breakdown of lysine. It may be ordered when a child has poor growth, feeding issues, unexplained acidosis, kidney problems, or when a metabolic disorder such as lysinuric protein intolerance is suspected. It can also help monitor known conditions over time.
Results are interpreted together with other urine and blood amino acids, kidney tests, clinical history, and diet. Finding the cause of an abnormal result can guide treatment, which may include dietary adjustments, management of kidney health, or further genetic evaluation.
Your result is compared with age-specific reference intervals that adjust for urine concentration using creatinine. A higher than expected value can reflect increased lysine loss in the urine, which may occur with certain kidney tubule disorders or inherited conditions. A lower than expected value is less commonly meaningful, and can be influenced by protein intake or overall nutrition.
If your result is outside the expected range, your clinician may repeat the test, review your diet and supplements, and order related studies such as plasma amino acids, urine organic acids, kidney function tests, or genetic testing based on your symptoms. Discuss any medications and recent illnesses, since these can affect kidney handling of amino acids. Decisions about treatment are based on the overall picture, not a single test.
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.
Spot urine is often used, but very concentrated or very dilute urine can still influence results even when adjusted to creatinine. Follow collection instructions and avoid excessive fluid loading just before the test.
High protein intake or lysine-containing supplements can transiently raise urinary lysine. Recent parenteral nutrition or specialized formulas may also affect the pattern of amino acids in urine.
Some drugs that can injure the proximal renal tubule, such as certain chemotherapies or antivirals, may cause generalized aminoaciduria with elevated urinary lysine. Always provide a full medication list.
Reference intervals vary by age because newborn and infant kidneys handle amino acids differently than older children and adults. Interpretation should always use the correct age bracket.
Improper storage or delayed processing can alter some amino acids. Laboratories often require prompt refrigeration or freezing; following instructions helps ensure accurate measurement.
Increased filtration during pregnancy can change urinary excretion patterns. If you are pregnant, your clinician may interpret results with additional context or recommend complementary tests.
References