Skip to content

Free Carnitine in Urine

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

This test measures the amount of free carnitine, a substance that helps transport fatty acids into cells for energy production, in your urine.

Quick summary

["Assessing free carnitine levels may help diagnose or monitor conditions affecting metabolism."]

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

Key facts at a glance

LOINC
26757-5
Short code
UC0
Synonyms
Carnitine Free Ur-aCnc
Category
chemistry
Sample
urine
Container
Sterile, leak-proof plastic urine collection container; 10–50 mL capacity screw-top vial without preservative. For pediatric collections, use pediatric urine collection bags.
Units
N/A
Ref low
2
Ref high
50
Fasting
false
Population
adult
Sex
all
Age range
0–999 years
Method
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS); also performed by enzymatic assay or HPLC
CPT
82017
SNOMED
44608007
Specimen volume
5–10 mL of random or 24-hour urine; minimum 1 mL acceptable for pediatric or limited samples
Stability
Stable at room temperature (15–25°C) for up to 24 hours; refrigerated (2–8°C) for up to 7 days; frozen at -20°C or below for up to 6 months. Avoid repeated freeze-thaw cycles. Ship on dry ice when transported to reference laboratories.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
72–168 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms or conditions linked to carnitine metabolism, such as muscle weakness, fatigue, or unexplained metabolic issues. It could also be part of a broader evaluation for inherited disorders like primary carnitine deficiency or mitochondrial disorders.

What to Expect Before the Test

No special preparation is typically needed. You may be asked to collect a urine sample in the morning or over a 24-hour period, depending on the instructions from your healthcare provider. Drink plenty of water to ensure adequate urine production.

What Happens During the Test

You will provide a urine sample, which is then sent to a lab for analysis. The test measures the concentration of free carnitine in your urine using a specialized laboratory technique.

What the Results Mean

Results are interpreted by your healthcare provider based on your clinical picture. Abnormal levels may indicate metabolic disorders or other conditions affecting carnitine metabolism, but they are not standalone diagnoses. Follow-up testing or additional evaluations may be needed.

Reference range

Reference values vary by laboratory methodology; urinary free carnitine (C0) excretion is typically expressed per mmol creatinine. Typical adult range: 2–50 mmol/mol creatinine. Age- and sex-specific pediatric ranges apply. Results should be interpreted in conjunction with acylcarnitine profile.N/A

Specimen: urine

No special preparation required. Patients should avoid excessive carnitine supplementation (e.g., L-carnitine, carnitine-containing infant formulas) for 24–48 hours prior to collection when clinically feasible, as supplementation significantly elevates urinary excretion. Maintain usual diet unless otherwise instructed.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Urine Free Carnitine

Frequently asked questions

What causes abnormal free carnitine levels?
Abnormal free carnitine levels in urine can result from genetic disorders affecting carnitine transport or metabolism, certain medications, or conditions like kidney disease. Always discuss any symptoms or concerns with your healthcare provider.
How is this test different from blood carnitine tests?
Urine free carnitine tests measure carnitine excreted in urine, which can reflect overall metabolic status and kidney function. Blood tests measure carnitine levels within your bloodstream, often used for different diagnostic purposes or to assess acute metabolic changes.
Can diet affect urine free carnitine test results?
Yes, dietary factors such as high-protein intake or certain supplements may influence carnitine levels. Follow your healthcare provider’s instructions regarding dietary restrictions before testing to ensure accurate results.
  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