Free Carnitine (Serum)
This test measures the amount of free carnitine, a compound that helps transport fatty acids into cells for energy production, in your blood serum.
["Free carnitine levels can help assess metabolic health, especially in conditions affecting fat metabolism."]
Key facts at a glance
- LOINC
- 18363-2
- Short code
- C0T
- Synonyms
- Carnitine Free Tiss-aCnt
- Category
- chemistry
- Sample
- serum
- Container
- Cryogenic screw-cap vial (tissue biopsy specimen container)
- Units
- N/A
- Ref low
- 1500
- Ref high
- 5000
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–99 years
- Method
- Tandem Mass Spectrometry (MS/MS)
- CPT
- 82379
- SNOMED
- 44635006
- Specimen volume
- 10-50 mg of fresh or frozen tissue (skeletal muscle, liver, or cardiac muscle)
- Stability
- Frozen at -20°C: up to 2 weeks; Frozen at -70°C or below: up to 6 months. Avoid repeated freeze-thaw cycles
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 72–168 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may order this test if you have symptoms or conditions related to fatty acid metabolism, such as muscle weakness, fatigue, or unexplained high levels of certain fats in your blood. It may also be used to monitor treatment for metabolic disorders like mitochondrial disorders or carnitine deficiency.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for 8–12 hours before the test if instructed by your provider. Bring any medications or supplements you’re taking, as they could affect results.
What the Test Involves
A blood sample will be drawn from a vein in your arm. The sample is sent to a lab for analysis. Free carnitine is measured using a specialized biochemical method to detect its concentration in your serum.
What the Results Mean
Results are compared to a reference range specific to your lab. Low levels may indicate carnitine deficiency or metabolic disorders, while very high levels could suggest muscle damage or certain genetic conditions. Your provider will discuss findings in the context of your health.
Reference range
Reference ranges vary by tissue type; consult laboratory-specific reference values. Typical muscle tissue: 1500-5000 nmol/g; typical liver tissue: 1000-3000 nmol/gN/A
No special preparation required. However, patients should avoid carnitine supplementation for 24 hours prior to specimen collection when clinically feasible, as this may affect results
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Free Carnitine
Frequently asked questions
What does a low level of free carnitine mean?
What does a high level of free carnitine mean?
How often should I get 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