24-Hour Urinary Free Carnitine
This test measures the amount of free carnitine in your urine over a 24-hour period. Free carnitine is a compound that helps transport fatty acids into cells for energy production.
["Assesses long-term carnitine levels in your urine, which can help diagnose or monitor conditions affecting fat metabolism."]
Key facts at a glance
- LOINC
- 34258-4
- Short code
- C0U24
- Synonyms
- Carnitine Free 24h Ur-sCnc
- Category
- chemistry
- Sample
- urine
- Container
- 24-hour urine collection container (sterile, preservative-free or with appropriate preservative such as thymol or 6N HCl depending on laboratory protocol)
- Units
- N/A
- Ref low
- 7
- Ref high
- 40
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- ≥ 0 years
- Method
- Tandem Mass Spectrometry (MS/MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
- CPT
- 82040
- SNOMED
- 408375005
- Specimen volume
- Complete 24-hour urine collection (minimum 10 mL aliquot from total volume)
- Stability
- Stable for 7 days at 2-8°C; for longer storage, freeze at -20°C or below for up to 6 months. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 48–168 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may recommend this test if you have symptoms like muscle weakness, fatigue, or unexplained weight changes, which could be linked to carnitine deficiencies or metabolic disorders. It’s also used in cases where other tests suggest issues with fatty acid metabolism.
What to Expect Before the Test
No special preparation is needed beyond collecting your urine over a full 24-hour period. You’ll typically start and end the collection at the same time each day, storing the urine in a refrigerator until you return it to the lab.
What to Expect During the Test
The lab will analyze the collected urine sample to measure free carnitine levels. Results are compared to reference ranges to identify any abnormalities.
Possible Results and Interpretation
Low levels of free carnitine in urine may indicate conditions like primary carnitine deficiency, mitochondrial disorders, or certain genetic metabolic disorders. High levels might suggest kidney issues or other metabolic imbalances. Your provider will discuss these findings with you.
Reference range
Reference ranges vary by laboratory and age; typically 7-40 mmol/mol creatinine in adults. Pediatric and neonatal ranges differ significantly.N/A
No special preparation required. Patient should maintain usual diet and hydration. Avoid collection during menstruation. Some medications (e.g., valproic acid, pivampicillin, carnitine supplements) may affect results.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Abnormal free carnitine levels in urine can signal underlying metabolic disorders, such as carnitine palmitoyltransferase (CPT) deficiencies, which impair fat metabolism. Early detection can guide treatment, such as dietary adjustments or supplements, to improve symptoms and prevent complications.
Short name
Free Carnitine Urine Profile
Frequently asked questions
What causes low free carnitine levels in urine?
What should I do if my test results are abnormal?
Can diet affect 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