Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
Lysine is an essential amino acid, one of the building blocks of proteins that your body cannot make on its own. This test measures the amount of lysine in your blood or urine, often as part of a broader quantitative amino acid panel. It helps show how your body absorbs, uses, and clears lysine.
Lysine supports growth, tissue repair, collagen formation, and the production of carnitine. Your sample may be a fasting blood draw or a urine specimen that is adjusted for creatinine to account for urine concentration.
Lysine levels can be affected by your protein intake, how well you absorb nutrients, and how your liver and kidneys function. The test is also important in evaluating rare inherited conditions that affect amino acid transport or metabolism. Clinicians may order it when there are concerns about growth, nutrition, developmental delays, seizures in infants, or when a metabolic disorder is suspected.
Results can help guide diagnosis, monitor nutrition or special formulas, and assess how well treatment plans are working. When interpreted with other amino acids, the test can provide a clearer picture of underlying health issues that influence protein balance.
Your result is interpreted alongside your age, the type of sample collected, and the pattern of other amino acids. A value outside the expected range does not always mean disease; recent meals, illness, or strenuous activity can shift amino acid levels. If results are unexpected, your clinician may repeat the test under fasting conditions and review your diet, supplements, and medications.
Depending on the clinical situation, next steps may include a full amino acid profile, urine organic acids, acylcarnitines, or genetic testing, as well as a nutrition assessment. If a hereditary metabolic condition is suspected, working with a metabolic specialist and a dietitian can help tailor management and follow-up.
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.
Protein-rich meals, amino acid drinks, or enteral/parenteral nutrition before the test can raise or alter lysine levels. A fasting sample is often recommended for the most reliable interpretation.
Lysine can be measured in plasma or urine, and results differ by specimen type. Morning fasting plasma and properly collected urine normalized to creatinine improve consistency.
Delayed processing, improper storage, or hemolysis can affect amino acid measurements. Prompt separation and freezing according to lab instructions help preserve accuracy.
Lysine supplements, high-protein shakes, and some therapies such as corticosteroids or total parenteral nutrition can influence results. Tell your clinician about all products you take.
Infection, fever, trauma, or recent surgery can change protein metabolism and shift amino acid patterns, including lysine, for a short period.
Reduced kidney or liver function can alter amino acid concentrations and urinary excretion. Urine results also depend on creatinine, which varies with muscle mass and hydration.
Expected values vary with age, especially in infants and children. Growth spurts and pregnancy can modestly change amino acid needs and circulating levels.
References