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Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
Methionine is an essential amino acid, meaning your body cannot make it and you must get it from food. It is a building block for proteins and a key source of methyl groups used to make many vital molecules through the S-adenosylmethionine (SAM) pathway. Your body also uses methionine to produce cysteine and related sulfur compounds that support antioxidant defenses.
This test measures the amount of methionine in your blood or urine. It is often included as part of an amino acid profile when doctors are evaluating nutrition, liver function, or possible inherited metabolic conditions that affect how amino acids are processed.
Measuring methionine helps your care team understand how your body is processing sulfur-containing amino acids. Results can aid in detecting certain rare metabolic disorders, guide assessment of nutritional status, and provide clues to liver function. In newborns and children, the test may be ordered to investigate abnormal screening results or symptoms that suggest an inborn error of metabolism.
In adults, methionine levels can be influenced by diet, supplements, and medical conditions. The test can help tailor dietary advice, evaluate parenteral nutrition, and guide follow-up testing such as other amino acids, vitamin levels, or genetic studies when needed.
Your result is interpreted in the context of your age, sample type, and clinical picture. Higher values can occur with increased intake of protein or certain supplements, with some metabolic conditions, or with liver dysfunction. Lower values may reflect limited intake, malabsorption, or other medical issues. For urine testing, the value is often compared with creatinine to account for concentration of the sample.
If your result is outside the expected range for your age or situation, your clinician may recommend a repeat fasting sample, a full amino acid profile, vitamin testing, liver studies, or consultation with a metabolic or genetics specialist. Always discuss results with your clinician, who will integrate them with your history, medications, and other labs before making decisions.
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.
Recent meals, especially high-protein foods, can raise methionine in blood. A fasting morning sample provides the most consistent interpretation, unless your clinician advises otherwise.
High-protein diets, protein powders, and products containing methionine or SAMe can increase levels. Vegetarian or restricted diets may lower intake and influence results.
These vitamins support sulfur amino acid metabolism. Deficiency or high-dose therapy can shift related pathways and alter methionine alongside other amino acids.
The liver is central to methionine metabolism. Liver inflammation or impaired function can lead to abnormal methionine levels even when diet is unchanged.
Urine methionine is often indexed to creatinine. Dehydration, very dilute urine, or kidney disease can affect the ratio and interpretation.
Parenteral nutrition, amino acid infusions, and some drugs or supplements can alter methionine. Tell your clinician about all therapies before testing.
Normal methionine levels vary with age, especially in infants and young children. Reference intervals are age-adjusted, and interpretation reflects this.
Delayed processing, improper storage, or significant hemolysis may affect amino acid measurements. Laboratories use specific handling to preserve accuracy.
Acute illness, fever, or catabolic states can change amino acid patterns. Your clinician may repeat testing after recovery for clarity.
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