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Carnitine, Serum Free (Total Carnitine Level)

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

This test measures the amount of free carnitine in your blood, an important molecule that helps carry fatty acids into cells for energy production.

Quick summary

["Free carnitine helps assess how well your body is using fats for energy and can indicate potential issues with fatty acid metabolism."]

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

Key facts at a glance

LOINC
16555-5
Short code
CARNCSF
Synonyms
Carnitine CSF-mCnc
Category
chemistry
Sample
csf
Container
Sterile CSF collection tube (polypropylene), tube #2 or #3 recommended to minimize blood contamination. Transport on ice or refrigerated.
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–120 years
Method
Tandem Mass Spectrometry (MS/MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
82017
SNOMED
104657004
Specimen volume
Minimum 0.5–1.0 mL of CSF; 1.0–2.0 mL preferred for adequate analysis
Stability
Refrigerated (2–8°C): stable for up to 24 hours; Frozen (-20°C or below): stable for up to 1 month. Avoid repeated freeze-thaw cycles.
Hemolysis max
200
TAT
72–168 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, especially if you have conditions like mitochondrial disorders, genetic metabolic disorders, or liver/kidney problems. It may also be used to monitor treatment for certain metabolic or genetic conditions.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw. Avoid strenuous activity or eating high-fat foods for optimal results.

What the Results Mean

Results are compared to a general reference range for healthy adults. Low levels might suggest impaired fatty acid metabolism, while very high levels could indicate liver disease or other metabolic issues. Your provider will discuss your specific results in the context of your health.

Common Conditions Linked to Carnitine Levels

Abnormal carnitine levels can be linked to conditions like carnitine palmitoyltransferase deficiency, mitochondrial disorders, or certain genetic metabolic diseases. Your doctor may also check carnitine levels if you have unexplained muscle weakness, heart issues, or neurological symptoms.

Reference range

Reference ranges for CSF carnitine are not well-established and may vary by laboratory. Generally, CSF carnitine levels are significantly lower than plasma levels. Reported typical values: Total carnitine 1.5–5.0 µmol/L; Free carnitine 1.0–4.0 µmol/L; Acylcarnitine ratio approximately 0.2–0.5. Consult laboratory-specific reference ranges.N/A

Specimen: csf

No special patient preparation is typically required. However, dietary intake and supplementation status may influence carnitine levels. Inform the laboratory of any recent carnitine supplementation or dietary changes.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Free Carnitine

Frequently asked questions

What causes low free carnitine levels?
Low free carnitine can result from genetic disorders affecting carnitine transport, liver or kidney disease, malnutrition, or certain medications. It may also appear in people with mitochondrial disorders or those who have undergone bariatric surgery.
What causes high free carnitine levels?
High free carnitine levels are less common but can occur in people with liver disease, severe dehydration, or certain metabolic disorders. Rarely, it may be linked to overuse of carnitine supplements.
How often should I get this test?
Your doctor will determine the frequency based on your health condition, treatment plan, or symptoms. Some people with chronic metabolic disorders may need this test regularly, while others may only need it occasionally.
  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