Free and Free Acyl Carnitine Profile (Urinary)
This test measures free carnitine and specific acyl carnitines in your urine, which helps assess how well your body is processing fats and certain amino acids.
["This test may help diagnose metabolic disorders linked to fat metabolism."]
Key facts at a glance
- LOINC
- 100428-2
- Short code
- CARNU
- Synonyms
- Carnitine + acylcarnitine Pnl Ur
- Category
- chemistry
- Sample
- serum
- Container
- Sterile urine collection container (no preservative) or cryogenic tube for aliquoted specimens
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–120 years
- Method
- Tandem Mass Spectrometry (MS/MS) with stable isotope dilution
- CPT
- 82017
- SNOMED
- 395195004
- Specimen volume
- 5-10 mL random or 24-hour urine collection
- Stability
- Refrigerated at 2-8°C for up to 7 days; frozen at -20°C or colder for long-term storage. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–168 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like fatigue, muscle weakness, or unexplained health issues that could be linked to metabolic disorders. It may also be used to monitor conditions affecting fat metabolism, such as certain genetic disorders or kidney function.
What the Test Measures
The test detects free carnitine (a molecule that helps transport fatty acids into cells) and various acyl carnitines (compounds formed when fats are broken down). Elevated or abnormal levels can indicate problems with fat metabolism.
Sample Collection and Preparation
You’ll provide a 24-hour urine sample collected in a special container. Follow your provider’s instructions carefully to ensure accurate results, as missing parts of the collection can affect the test.
What to Expect Before the Test
No special preparation is typically needed, but avoid certain medications or supplements that might interfere with results. If you’re pregnant, have kidney disease, or take medications like carnitine supplements, let your provider know.
Reference range
Reference ranges vary by individual acylcarnitine species and laboratory. Free carnitine, total carnitine, and individual acylcarnitines are reported with age-specific and species-specific reference intervals. Acylcarnitine panel typically includes C0 (free carnitine), C2, C3, C4, C5, C6, C8, C10, C12, C14, C16, C18, and related species. Results should be interpreted in conjunction with clinical findings.N/A
No special preparation required. Patients on carnitine supplementation should consult their physician regarding whether to discontinue prior to testing. Dietary intake may influence acylcarnitine profiles; fasting is not required but a recent meal may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal results may signal metabolic disorders, such as medium-chain acyl-CoA dehydrogenase (MCAD) deficiency or other inherited conditions affecting fat metabolism. High levels of specific acyl carnitines can also indicate kidney problems or exposure to toxins. Your provider will interpret results in the context of your symptoms and medical history.
Short name
Free/acyl carnitine urine test
Frequently asked questions
What causes abnormal results in this test?
How long does it take to get results?
Can I fast before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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