Platform
Company
Immunology & Autoimmune
Review status
Currently under review
Pending specialist review and validation.
C5:1 Tiglyl/Methylcrotonyl is an acylcarnitine measured in blood using tandem mass spectrometry. It reflects small molecules formed when your body breaks down certain amino acids, mainly isoleucine and leucine. The measurement captures the combined signal of tiglylcarnitine and methylcrotonylcarnitine that circulate attached to carnitine.
This marker is part of expanded acylcarnitine profiles used in newborn screening and in evaluations for inherited metabolic disorders. It helps clinicians understand how your body handles energy from protein, especially during stress, illness, or fasting.
Changes in C5:1 can point to inborn errors of metabolism that affect pathways for processing branched‑chain amino acids, such as beta‑ketothiolase deficiency and related organic acidemias. Levels can also shift during acute illness, poor intake, or other metabolic stress, so results are interpreted in clinical context.
Your clinician may order this test after an abnormal screen, if you or your child has unexplained vomiting, low energy, or developmental concerns, or to monitor a known metabolic condition. Identifying a true metabolic disorder allows tailored care, including nutrition strategies, avoidance of prolonged fasting, and plans for managing illness safely.
A single mild elevation does not always mean disease. Your result is interpreted alongside other acylcarnitines, urine organic acids, and your symptoms and exam. If the value is above the usual limits, your clinician may repeat testing when you are well or after feeding, and may add confirmatory studies such as urine organic acids, acylglycines, enzyme or genetic testing.
Persistent or clearly abnormal patterns suggest a metabolic condition and warrant evaluation by a metabolic specialist. If you or your child becomes unwell with poor feeding, vomiting, unusual sleepiness, or dehydration, seek care promptly since metabolic stress can worsen. Most identified conditions can be managed with nutrition plans, sick day instructions, and sometimes carnitine or other supplements.
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.
Illness, dehydration, or fasting increases breakdown of fat and protein, which can raise certain acylcarnitines, including C5:1. Testing when recovered often gives a clearer baseline.
Metabolism changes rapidly in the first days to weeks of life. Prematurity and the timing of the sample after birth can influence acylcarnitine patterns and may prompt repeat testing.
Drugs that affect carnitine metabolism, such as valproate or pivalate‑containing antibiotics, and L‑carnitine supplements can alter acylcarnitine results. Tell your clinician what you take.
Very high protein intake, unusual amino acid formulas, or prolonged poor intake can change C5:1 levels. Follow your usual diet unless your clinician advises otherwise.
Hemolysis, improper drying of a blood spot, delayed processing, or storage issues can affect measured acylcarnitines. Proper collection and handling reduce analytic variability.
In newborns, maternal carnitine status, diet, and supplements can influence the infant’s acylcarnitine profile early after birth. This may normalize on repeat testing.
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