Free Carnitine (Serum)
This test measures the level of free carnitine, a compound that helps transport fatty acids into cells for energy production. It’s often checked in connection with metabolic or genetic conditions.
["Free carnitine helps cells use fat for energy and may be important in diagnosing certain metabolic disorders."]
Key facts at a glance
- LOINC
- 53095-6
- Short code
- C0FCN
- Synonyms
- Carnitine Free SFr DBS
- Category
- chemistry
- Sample
- serum
- Container
- Whatman 903 filter paper (or equivalent FDA-approved newborn screening filter paper); Dried blood spot (DBS) specimen collection device; Five fully saturated blood spots required; Allow to air-dry horizontally for ≥3 hours at room temperature before transport; Note: LOINC 53095-6 may also be applied to serum/plasma matrices in some laboratory implementations.
- Units
- N/A
- Ref low
- 0.7
- Ref high
- 1
- Critical range
- 0.4 N/A – —
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 0–150 years
- Method
- Tandem Mass Spectrometry (MS/MS) with stable isotope dilution; flow-injection analysis (FIA-MS/MS)
- CPT
- 82017 (Acylcarnitines; quantitative, each specimen) or 83789 (Carnitine, total and free, quantitative, each specimen) — note: CPT coding for DBS acylcarnitine profiles may be reported under 82017 or specific newborn screening codes; Confirm with local laboratory coding policies.
- SNOMED
- 44778007 |Free carnitine measurement| ; 365666009 |Carnitine measurement| ; 44608003 |Dried blood spot specimen| ; 46662006 |Newborn screening procedure| ; Cross-reference with local laboratory-specific SNOMED CT extensions.
- Specimen volume
- ≥5 fully saturated blood spots (approximately 50-75 µL blood per spot, totaling 250-375 µL); Each spot should be evenly saturated and fill the pre-printed circle; Minimum total blood volume approximately 100 µL (≥3 spots acceptable for repeat analysis).
- Stability
- Stable for 7 days at room temperature (20-25°C) on filter paper; Stable for 14 days at 2-8°C; Stable for ≥30 days at -20°C or below; Avoid exposure to heat (>37°C), humidity (>50% relative humidity), and direct sunlight; Specimen integrity may be compromised if improperly dried, exposed to moisture, or stored above recommended temperatures; Transport at ambient temperature in protective mailing envelope; Avoid freeze-thaw cycles after drying.
- 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 a free carnitine test if you have symptoms like fatigue, muscle weakness, or unexplained health issues. It could also be part of evaluating conditions like mitochondrial disorders, carnitine deficiency, or metabolic diseases such as medium-chain acyl-CoA dehydrogenase (MCAD) deficiency.
What to Expect Before the Test
No special preparation is usually needed, but you may be asked to fast for 8–12 hours before the test if instructed. Bring any medications or supplements you’re taking, as they could affect results.
What Happens During the Test
A blood sample will be drawn from a vein in your arm. The process is quick and typically painless. The sample is sent to a lab for analysis using a high-performance liquid chromatography (HPLC) method.
What the Results Mean
Results are compared to a reference range, but exact values can vary by lab. Low levels may suggest carnitine deficiency or metabolic disorders, while very high levels could indicate muscle breakdown or certain liver conditions. Your provider will interpret results in the context of your overall health.
Reference range
Free carnitine (C0): 20-60 µmol/L (DBS); Total carnitine: 45-95 µmol/L (DBS); C0/Total ratio: >0.70 (ratio interpretation varies by acylcarnitine profile context); Reference values may differ by laboratory and age; consult performing laboratory report.N/A
Fasting is not required, but fasting (2-4 hours) is recommended for optimal interpretation, especially for acylcarnitine profile evaluation in suspected fatty acid oxidation disorders; Avoid exogenous carnitine supplementation for 24-48 hours prior to sampling when investigating primary carnitine deficiency (consult ordering physician); Newborn screening samples are typically collected 24-72 hours after birth via heel stick; Standard DBS sample collection via fingerstick or heelstick following approved procedures; Sample should be completely dried before storage or transport.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
Free Carnitine
Frequently asked questions
What could cause abnormal results?
How often should I get this test?
Can diet or supplements 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