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.
["Free carnitine levels can help diagnose or monitor conditions affecting fat metabolism."]
Key facts at a glance
- LOINC
- 53233-3
- Short code
- C0C16
- Synonyms
- Carnitine Free/C16 DBS-sRto
- Category
- chemistry
- Sample
- serum
- Container
- Dried blood spot (DBS) collection card - Whatman 903 or equivalent filter paper
- Units
- N/A
- Ref low
- 0
- Ref high
- 100
- Critical range
- — – 100 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–99 years
- Method
- Tandem Mass Spectrometry (MS/MS)
- CPT
- 82017
- SNOMED
- 44608000
- Specimen volume
- 5-10 μL whole blood per spot (minimum 3 filled circles)
- Stability
- Dried blood spots stable at room temperature (15-25°C) for up to 30 days; at 2-8°C for up to 90 days; at -20°C for long-term storage up to 1 year
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–168 hours
- Order
- routine
Why This Test Might Be Ordered
Your healthcare provider may order this test if you have symptoms of metabolic disorders, such as muscle weakness, fatigue, or unexplained weight changes. It may also be used to check for conditions like mitochondrial disorders, carnitine deficiency, or disorders of fatty acid metabolism.
What to Expect Before the Test
No special preparation is usually needed. You may be asked to fast for a few hours before the test, but always follow your provider’s instructions. Bring any medications you’re currently taking, as some may affect results.
How the Test Is Performed
A blood sample is drawn from a vein, typically in your arm, by a healthcare professional. The blood is then sent to a lab for analysis.
What the Results Mean
Results are interpreted by your healthcare provider based on your symptoms, medical history, and other test results. Abnormally low or high levels may indicate underlying health issues that need further evaluation.
Reference range
C0/C16 molar ratio < 100 (suggestive of CPT II deficiency when elevated); specific reference values vary by laboratory and ageN/A
No special preparation required. Patient should be in a metabolically stable state; avoid specimen collection during acute illness or prolonged fasting when possible, as this may affect carnitine/acylcarnitine ratios.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Low levels of free carnitine can suggest conditions like primary carnitine deficiency, mitochondrial disorders, or certain genetic metabolic disorders. High levels may be seen in conditions involving excessive fat breakdown, such as severe muscle damage or certain types of diabetes. Your provider will use these results alongside other tests and clinical findings to guide diagnosis and treatment.
Short name
Free Carnitine
Frequently asked questions
What causes free carnitine levels to be low?
What are the common symptoms of low carnitine levels?
How is free carnitine treated?
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