Amino Acids (Plasma)

Proline is an amino acid measured in dried blood spot (DBS) samples, typically as part of newborn screening panels for metabolic disorders. Abnormal proline levels are associated with hyperprolinemia, a rare genetic metabolic condition affecting amino acid breakdown. Two types exist: Type I causes neurological problems, while Type II is usually asymptomatic. Early detection through newborn screening allows monitoring and intervention if needed.

Gamma-aminobutyric acid (GABA) is a neurotransmitter that helps regulate nervous system activity. This urine test measures GABA levels adjusted for creatinine to account for urine concentration. GABA abnormalities may be associated with neurological conditions, seizure disorders, or metabolic imbalances. Testing GABA in urine can help evaluate neurological health and assess certain brain-related conditions, though interpretation requires clinical context.

Isoleucine is an essential amino acid your body cannot produce and must obtain from dietary protein. This qualitative test screens for abnormal isoleucine levels, which may indicate metabolic disorders affecting amino acid processing. Elevated isoleucine can suggest conditions like maple syrup urine disease or branched-chain ketoaciduria, while low levels may reflect protein malnutrition or liver disease. Results help identify metabolic disorders and nutritional status.

Valine is an essential amino acid your body cannot produce and must obtain from foods like meat, dairy, nuts, and legumes. This urine test measures valine levels and is typically used in genetic metabolic screening, particularly for amino acid metabolism disorders. Abnormal urine valine levels can indicate conditions like maple syrup urine disease (MSUD) or other inherited metabolic disorders affecting amino acid processing. Early detection through newborn screening or in symptomatic individuals is critical, as these conditions can cause serious neurological problems if untreated.

Glycine is an amino acid found in protein-containing foods and produced by your body. This urine test measures 24-hour glycine excretion and is used in genetic metabolic screening. Abnormal glycine levels can indicate several inherited disorders, including primary hyperoxaluria, glycine encephalopathy, or other amino acid metabolism disorders. These conditions can cause kidney stones, neurological problems, or developmental delays if undiagnosed. Testing is often part of newborn screening or evaluation of children with unexplained developmental delay, kidney disease, or seizures.

Phenylalanine is an essential amino acid found in protein-rich foods. This urine test measures 24-hour phenylalanine excretion and screens for phenylketonuria (PKU), an inherited metabolic disorder where the body cannot properly break down phenylalanine. PKU causes intellectual disability if undetected and untreated in infancy. Elevated urinary phenylalanine indicates high blood phenylalanine levels, requiring a specialized low-phenylalanine diet. Most newborns are screened for PKU at birth, but this test may be used in older children or adults with suspected metabolic disease or developmental concerns.

Taurine is an amino acid important for heart, brain, and eye function. This urine test measures taurine levels and is primarily used in genetic metabolic screening and evaluation of inherited amino acid disorders. Abnormal taurine levels can indicate several metabolic conditions, including defects in taurine synthesis or transport. Some conditions associated with low taurine include cardiomyopathy, retinal degeneration, and developmental problems. Identifying taurine deficiency allows for dietary supplementation, which can prevent or slow disease progression, particularly cardiac and ophthalmologic complications.

Arginine is an amino acid important for protein synthesis, immune function, and blood vessel health. This test measures arginine on a dried blood spot (from a heel prick), commonly used in newborn screening. Elevated blood arginine levels can indicate several inherited metabolic disorders, including argininemia (argininase deficiency) and other urea cycle disorders. These rare genetic conditions cause intellectual disability, seizures, and progressive neurological problems if untreated. Early detection through newborn screening allows for dietary management and medical treatment to prevent serious complications. This test may also be ordered in older individuals with neurological symptoms or family history of metabolic disease.

Threonine is an essential amino acid your body cannot produce on its own and must obtain from food. A urine threonine test measures the amount of this amino acid being excreted in your urine, which can reflect your body's amino acid metabolism and nutritional status. Abnormal levels may indicate metabolic disorders, kidney dysfunction, or nutritional imbalances. This test is often used in genetic metabolic screening, particularly in newborns and individuals with suspected amino acid metabolism disorders.

Glutamate is a non-essential amino acid and a key neurotransmitter in the brain. A 24-hour urine glutamate test measures how much of this amino acid your body is excreting over a full day. Elevated urinary glutamate may indicate metabolic disorders, kidney disease, or neurological conditions. Abnormally low levels could suggest nutritional deficiencies or absorption problems. This test provides insight into your amino acid metabolism and overall metabolic health.

Serine is a non-essential amino acid that your body synthesizes from other compounds and also obtains from food. A urine serine test measures how much of this amino acid is being excreted in your urine, reflecting your body's amino acid metabolism and nutritional status. Abnormal serine levels may indicate genetic metabolic disorders, kidney dysfunction, or nutritional imbalances. This test is most commonly used in newborn screening and evaluation of suspected inherited metabolic diseases.

Leucine is an essential branched-chain amino acid crucial for muscle protein synthesis and energy metabolism. A 24-hour urine leucine test measures how much of this amino acid your body is excreting over a full day. Abnormal urinary leucine levels may indicate inherited metabolic disorders like maple syrup urine disease (MSUD), kidney dysfunction, or severe nutritional deficiencies. This test is particularly important in newborn screening and evaluation of patients with neurological symptoms or developmental delays.

Sarcosine is a naturally occurring amino acid produced by your body's metabolism of choline. A 24-hour urine sarcosine test measures how much of this compound you are excreting. Elevated levels may indicate certain metabolic disorders, nutritional imbalances, or kidney dysfunction. Sarcosine has also been investigated for its potential role in neurological conditions like schizophrenia. This test is less commonly ordered but may be used in specialized metabolic or psychiatric evaluations.

Tryptophan is an essential amino acid your body obtains from dietary protein and cannot produce on its own. This qualitative test screens for abnormal tryptophan levels, which may indicate nutritional deficiency, malabsorption, liver disease, or rare metabolic disorders. Tryptophan is important for producing serotonin, a neurotransmitter affecting mood and sleep, and niacin, a B vitamin essential for energy metabolism. Abnormalities may affect mental health, immune function, and overall protein metabolism.

Histidine is an essential amino acid required for protein synthesis, immune function, and tissue repair. A urine histidine test measures how much histidine your body is excreting, reflecting nutritional intake, protein metabolism, and kidney function. Elevated urinary histidine may indicate excessive protein intake, kidney disease, or rare metabolic disorders. Low levels may suggest nutritional deficiency or malabsorption. This test helps assess amino acid metabolism and nutritional status.

Hydroxyproline is an amino acid found almost exclusively in collagen, the structural protein in skin, bones, joints, and connective tissue. This qualitative test screens for abnormal hydroxyproline levels, which may indicate collagen metabolism disorders, bone disease, liver disease, or connective tissue problems. Elevated levels can reflect increased collagen breakdown (from arthritis or injury) or impaired collagen synthesis. This test helps assess bone and connective tissue health.

Tyrosine is a non-essential amino acid your body can produce from the amino acid phenylalanine. A urine tyrosine test measures how much is being excreted, reflecting protein metabolism and kidney function. Elevated urinary tyrosine may indicate excessive protein intake, kidney disease, or rare metabolic disorders like tyrosinemia. Low levels may suggest nutritional deficiency or malabsorption. This test helps assess amino acid metabolism and protein status.

Methionine is an essential amino acid obtained from dietary protein that plays a key role in protein synthesis and methylation reactions vital for cell function. A urine methionine test measures excretion levels, reflecting protein metabolism and kidney function. Elevated levels may indicate excessive protein intake, kidney disease, or metabolic disorders. Low levels may suggest nutritional deficiency, malabsorption, or liver disease. This test helps assess amino acid metabolism and nutritional status.

Alpha-aminobutyrate (also called 2-aminobutyrate) is a non-standard amino acid produced during protein metabolism. A 24-hour urine test measures excretion levels, which may be elevated in certain metabolic disorders, liver disease, or kidney dysfunction. Abnormal levels are relatively uncommon but may indicate serious metabolic or organ problems. This test is often ordered as part of amino acid profiling in patients with unexplained metabolic symptoms or suspected genetic metabolic disorders.

Ornithine is an amino acid involved in the urea cycle, which helps your body process and eliminate nitrogen waste. Measuring ornithine levels in blood helps assess amino acid metabolism and can identify rare genetic metabolic disorders. Abnormally high ornithine levels may indicate urea cycle disorders or other metabolic conditions, while very low levels are uncommon but can signal specific genetic defects. This test is typically ordered when metabolic or genetic screening is warranted.

Glutamine is an amino acid excreted in urine; elevated levels can reflect kidney function changes or metabolic stress. Urinary glutamine measurement helps assess nitrogen metabolism and kidney handling of amino acids. Abnormal levels may indicate metabolic disorders, kidney dysfunction, or systemic illness affecting amino acid metabolism. This test is sometimes used in specialized metabolic screening or when investigating unusual urine composition.

Lysine is an essential amino acid required for protein synthesis, immune function, and calcium absorption. This test measures plasma lysine levels to screen for genetic amino acid metabolism disorders, particularly in newborns or patients with unexplained developmental delays or neurological symptoms. Abnormal lysine levels indicate inborn errors of metabolism affecting how the body processes amino acids. Early detection allows dietary management and supplementation to prevent serious neurological complications and developmental problems.

Homocystine is the oxidized dimer form of homocysteine, an amino acid involved in protein metabolism. This plasma-only test measures homocystine to assess cardiovascular risk and screen for homocysteine metabolism disorders. Elevated levels indicate increased risk for blood clots, heart disease, and stroke, and may reflect deficiencies in vitamins B12, B6, or folate, or genetic metabolic disorders. This test helps identify cardiovascular risk and metabolic conditions treatable with B-vitamin supplementation or dietary changes.

Citrulline is an amino acid involved in the urea cycle, which processes nitrogen waste in your body. Urine citrulline levels reflect your body's amino acid metabolism and kidney filtration. Abnormal citrulline levels can indicate genetic metabolic disorders affecting amino acid processing, kidney disease, or nutritional deficiencies. This test is most commonly ordered when metabolic disorders are suspected or during investigation of unexplained symptoms like developmental delays, seizures, or organ dysfunction.

Asparagine is an amino acid important for protein synthesis and cellular function. Urine asparagine levels reflect your body's amino acid metabolism and kidney function. Abnormal asparagine levels may indicate genetic metabolic disorders affecting amino acid processing, kidney disease, or nutritional imbalances. This test is typically ordered when investigating unexplained developmental delays, seizures, or when rare metabolic disorders are suspected.

This test measures cystathionine, an amino acid intermediate in the methionine metabolism pathway, in urine. Elevated cystathionine can indicate cystathionine beta-synthase (CBS) deficiency, a rare genetic metabolic disorder that disrupts amino acid processing. This condition can lead to neurological problems, lens dislocation, and cardiovascular complications. Early detection through urine screening allows for dietary management and supplementation to prevent complications.

This test measures 1-methylhistidine, a modified amino acid, in serum or plasma. This amino acid is a product of muscle protein metabolism and dietary intake, particularly from meat. Elevated serum levels may indicate increased muscle protein turnover or dietary influences. It is used as a marker of dietary protein intake and muscle catabolism, and may be part of broader amino acid profiling panels for metabolic assessment.

Alanine is an amino acid important for muscle metabolism, energy production, and immune function. A urine alanine test measures urinary excretion and may indicate amino acid metabolism disorders or specific medical conditions. Abnormal levels can suggest genetic metabolic disorders, liver disease, or muscle wasting. This specialized test is typically ordered when amino acid metabolism disorders are suspected, and results are interpreted alongside plasma amino acid levels and clinical symptoms.

3-Methylhistidine is an amino acid derivative found primarily in muscle protein. serum or plasma testing measures this compound in the fluid surrounding the brain and spinal cord. This is a specialized test used by metabolic specialists to diagnose rare genetic amino acid disorders affecting the nervous system. Results are interpreted by specialists in metabolic and neurological conditions.

Beta alanine is an amino acid that appears in urine when levels are elevated in the body. Elevated urinary beta alanine can indicate genetic disorders affecting amino acid metabolism, kidney dysfunction, or carnitine deficiency. This test is often part of newborn screening or metabolic panels to detect inherited metabolic disorders early, allowing for prompt intervention and management.

Ethanolamine is a compound found in blood that plays a role in cell membrane structure and lipid metabolism. Elevated or abnormal ethanolamine levels may indicate metabolic disorders, liver dysfunction, or certain genetic conditions affecting lipid synthesis. This test is sometimes used in specialized metabolic screening panels to evaluate unusual symptoms or suspected inborn errors of metabolism.

This test measures the proportion of cholesterol in HDL 3b, a specific subclass of HDL (good cholesterol), relative to total HDL. HDL subclasses have different protective properties for cardiovascular health—larger HDL particles tend to be more cardioprotective than smaller ones. This advanced lipid test provides more detailed information about your cholesterol profile than standard HDL testing, potentially offering better insight into cardiovascular risk and the effectiveness of lipid-lowering therapies.

Birth date is your date of fetal delivery, representing the day you were born. This is a fundamental demographic data point used in healthcare for calculating age, determining age-appropriate health screenings and interventions, and maintaining accurate medical records. Birth date is required for personalized medicine—many test result interpretations, medication dosing recommendations, and health risk assessments vary based on age. Accurate birth date documentation ensures you receive age-appropriate preventive care.