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Acylcarnitineserplql

Published: August 9, 2026Updated: August 16, 2026

A blood test that measures acylcarnitine levels to screen for metabolic disorders affecting how the body processes fats for energy.

Quick summary

{"Screens for fatty acid oxidation disorders and organic acidemias","Commonly used in newborn screening programs","Abnormal results may indicate a metabolic condition requiring treatment","The test helps doctors diagnose rare but serious inherited disorders","Early detection allows for proper management and prevention of complications"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
31991-3
Short code
ACY
Synonyms
Acylcarnitine SerPl Ql
Category
chemistry
Sample
serum
Container
Serum separator tube (SST/gold top) or plain red top tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Tandem Mass Spectrometry (MS/MS)
CPT
82017
SNOMED
313371009
Specimen volume
1.0 mL minimum, 2.0 mL preferred for adequate testing
Stability
Room temperature: 24 hours; Refrigerated (2-8°C): 7 days; Frozen (-20°C or below): 30 days. Avoid repeated freeze-thaw cycles.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
48–96 hours
Order
routine

What is this test?

The acylcarnitine test measures the presence and levels of acylcarnitines in your blood. Acylcarnitines are substances produced when the body breaks down fatty acids for energy. This test helps detect metabolic disorders where the body cannot properly process fats, leading to a buildup of certain acylcarnitines in the blood.

How is the test performed?

A healthcare professional will draw a small blood sample from a vein in your arm or, for newborns, from a heel stick. The blood is collected on a special filter paper and sent to a laboratory for analysis. No special preparation is typically required, though your doctor may ask about recent meals or medications.

What conditions does this test detect?

The acylcarnitine test primarily screens for inherited metabolic disorders, including: medium-chain acyl-CoA dehydrogenase (MCAD) deficiency, carnitine palmitoyltransferase (CPT) deficiencies, and various organic acidemias. These conditions affect how the body converts fat into energy and can cause serious health problems if not treated early.

What do the results mean?

Normal results mean no abnormal levels of acylcarnitines were detected. Abnormal results may indicate a metabolic disorder, but further testing is usually needed to confirm a specific diagnosis. Your healthcare provider will interpret the results in the context of your symptoms, medical history, and other test results.

Reference range

Not Detected - The presence of abnormal acylcarnitine profiles may indicate inborn errors of metabolism such as fatty acid oxidation disorders, organic acidemias, or carnitine transport defects.N/A

Specimen: serum

No special preparation required. This test can be performed without fasting. Inform the laboratory of any medications, supplements, or recent parenteral nutrition as these may affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings2

Frequently asked questions

Why is this test done on newborns?
Many metabolic disorders are not apparent at birth but can cause severe health problems within the first days or weeks of life. Newborn screening allows detection and treatment before symptoms develop, significantly improving outcomes. MCAD deficiency and other fatty acid oxidation disorders can be fatal in otherwise healthy-appearing newborns if not diagnosed early.
Does abnormal mean my baby definitely has a disorder?
No, an abnormal result does not always mean a definite diagnosis. The initial test is a screening tool, and abnormal results require follow-up testing, including repeat acylcarnitine analysis and possibly genetic testing, to confirm a diagnosis. False positives can occur due to sample handling issues or other factors.
Is fasting required before the test?
For newborns and infants, fasting is not typically required as part of the screening. For older children or adults undergoing diagnostic testing, your healthcare provider may recommend fasting for 8-12 hours before the blood draw, as this can help reveal certain abnormalities more clearly. Always follow your doctor's specific instructions.
What happens if a disorder is diagnosed?
If a metabolic disorder is confirmed, treatment typically involves dietary modifications such as avoiding fasting, special low-fat diets, carnitine supplementation, and careful management during illness. With early and ongoing treatment, individuals with these disorders can lead relatively normal, healthy lives. A metabolic specialist will guide long-term management.
  1. 1
    Mayo Clinic - Newborn Screening TestsSource
  2. 2
    MedlinePlus - AcylcarnitineSource
  3. 3
    American College of Medical Genetics - Newborn ScreeningSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy