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Free Carnitine (Serum/Plasma)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of free carnitine, a compound that helps transport fatty acids into cells for energy production. Free carnitine levels can be checked to assess metabolic health, especially in conditions involving fatty acid metabolism.

Quick summary

["Free carnitine helps your body use fat for energy and supports healthy metabolism."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
10877-9
Short code
CARN-C0
Synonyms
Carnitine Free Ur-mCnc
Category
chemistry
Sample
urine
Container
Sterile, screw-capped urine container; preferably a 24-hour urine collection container without preservatives or with appropriate preservative per laboratory requirements.
Units
N/A
Ref low
0
Ref high
50
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
82017
SNOMED
385458005
Specimen volume
10-50 mL for random urine; complete 24-hour collection for timed specimens. Minimum 1 mL required for analysis.
Stability
Stable for 7 days at 2-8°C; stable for longer periods at -20°C or below. Avoid repeated freeze-thaw cycles. If delayed analysis, freeze specimen promptly.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
48–168 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order a free carnitine test if you have symptoms like muscle weakness, fatigue, or unexplained weight changes. It may also be used to monitor conditions affecting carnitine metabolism, such as inherited disorders or certain metabolic syndromes. Rarely, it could be part of a broader evaluation for unexplained muscle pain or nerve issues.

What Does a Result Mean?

Results may vary depending on your health status and the reason for testing. While reference ranges can differ by lab, very low levels might suggest a metabolic disorder, while very high levels could indicate kidney problems or certain medications. Your doctor will interpret results in the context of your overall health.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The blood is then processed to separate the serum or plasma, where free carnitine is measured using a specialized laboratory technique, often high-performance liquid chromatography (HPLC).

What Can Affect Results?

Several factors may influence free carnitine levels, including certain medications (like some antibiotics or anticonvulsants), kidney function, diet, and underlying metabolic conditions. Avoiding certain foods or supplements for a few days before testing may help ensure accurate results.

Reference range

Reference ranges vary by laboratory; generally reported per creatinine ratio. Typical urinary free carnitine (C0) excretion: 0-50 μmol/mmol creatinine (random urine) or 10-70 μmol/day (24-hour urine). Pediatric and adult ranges differ. Consult laboratory-specific reference values.N/A

Specimen: urine

No fasting required. Patient should maintain usual diet prior to collection. Avoid vigorous exercise before specimen collection. Inform laboratory of any carnitine supplementation, as this may significantly affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Carnitine

Frequently asked questions

How long does it take to get results from this test?
Test results are typically available within 1 to 3 business days, depending on your lab’s processing schedule. Your healthcare provider will contact you with the results once they are ready.
What are the common symptoms linked to abnormal free carnitine levels?
Symptoms of low free carnitine may include muscle weakness, fatigue, heart palpitations, or unexplained weight loss. Symptoms of high free carnitine levels are less common but may include nausea, vomiting, or signs of kidney issues like swelling or frequent urination. Always discuss symptoms with your doctor.
Can diet or supplements affect free carnitine test results?
Yes, certain foods and supplements can influence carnitine levels. High-fat diets or supplements containing carnitine (like L-carnitine) may temporarily alter results. Your doctor may advise dietary restrictions or timing around testing to ensure accurate findings.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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