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Free Serum Carnitine (Total Carnitine Level)

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, in your serum.

Quick summary

["Assessing free carnitine levels can help identify metabolic issues or deficiencies."]

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

Key facts at a glance

LOINC
32613-2
Short code
C0/CARNT-UR
Synonyms
Carnitine Free SFr Ur
Category
chemistry
Sample
urine
Container
Sterile urine collection container
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 years
Method
Tandem Mass Spectrometry (MS/MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
82017
SNOMED
44608005
Specimen volume
10-20 mL of random or 24-hour urine
Stability
Stable for 7 days at 2-8°C when refrigerated; stable for longer periods at -20°C or below
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
24–168 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may order this test if you have symptoms like fatigue, muscle weakness, or unexplained problems with energy production. It could also be part of evaluating conditions such as mitochondrial disorders, certain genetic metabolic diseases, or liver/kidney disorders that affect carnitine metabolism.

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 heavy meals that day. Tell your provider about any medications you’re taking, as some may affect results.

How the Test Is Performed

A blood sample is taken from a vein in your arm. You may feel a small pinch when the needle is inserted, but the procedure is quick. The blood is sent to a lab for analysis using a method like high-performance liquid chromatography (HPLC) to separate and measure free carnitine levels.

What the Results Mean

Results are typically reported as a concentration in micromoles per liter (µmol/L). Higher or lower-than-expected levels may indicate underlying health concerns, but interpretation depends on clinical context and your overall health. Your provider will discuss findings with you.

Reference range

Free carnitine (C0) reference ranges vary by age. Reference range for free carnitine/total carnitine ratio is typically >0.7 in healthy individuals. Decreased ratios may indicate primary or secondary carnitine deficiency.N/A

Specimen: urine

No special preparation required. Patient should maintain normal diet prior to collection. Avoid excessive consumption of carnitine-rich foods (red meat, dairy) 24 hours prior to collection if clinically indicated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Elevated free carnitine levels may suggest conditions like mitochondrial disorders, certain liver diseases, or excessive exercise-related muscle breakdown. Low levels could indicate carnitine deficiency, genetic metabolic disorders, or impaired transport of fatty acids into cells. Always correlate results with symptoms and other tests for accurate diagnosis.

Short name

Free Carnitine Test

Frequently asked questions

What causes free carnitine levels to be high?
High free carnitine levels can occur due to conditions affecting fat metabolism, such as mitochondrial disorders, certain liver diseases, or prolonged, intense exercise. It may also be seen in people with kidney disease or those taking certain medications that alter carnitine metabolism.
Can diet affect free carnitine test results?
Dietary factors like high-protein or high-fat meals may temporarily influence carnitine levels, but fasting is usually recommended before testing to avoid variability. Avoiding extreme exercise or stress on the day of testing can also help ensure accurate results.
How often should this test be repeated?
The frequency depends on your symptoms and diagnosis. If you have a known metabolic condition, your provider may recommend periodic monitoring. If this test is part of routine screening, follow their guidance for follow-up testing.
  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