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Free Carnitine in 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. It may be checked if you have symptoms of metabolic or muscle disorders.

Quick summary

["Free carnitine helps cells use fat for energy; low levels may signal metabolic or muscle issues."]

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

Key facts at a glance

LOINC
16556-3
Short code
Carnitine Amn-mCnc
Synonyms
Carnitine Amn-mCnc
Category
chemistry
Sample
fluid
Container
Sterile tube
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
2-5 mL
Stability
Room temperature: 2h, Refrigerated: 24h
Hemolysis max
300
TAT
4–24 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. It could also be part of a broader evaluation for conditions affecting metabolism, such as mitochondrial disorders or inherited carnitine deficiencies.

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 you’re taking to your appointment.

What the Test Involves

A blood sample will be drawn from a vein in your arm. This is a quick, painless procedure that typically takes a few minutes. The sample is sent to a lab for analysis.

What the Results Mean

Results may be compared to a reference range provided by your lab, but exact values can vary by lab. Low levels might indicate a deficiency or metabolic disorder, while high levels could signal kidney issues or other conditions.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Carnitine

Frequently asked questions

How often should I get this test?
This test is usually ordered as needed, depending on your symptoms or medical condition. Your provider will determine how often follow-up testing is required.
What causes low free carnitine levels?
Low free carnitine can result from genetic disorders, certain medications, kidney disease, or conditions that impair fat metabolism. If you suspect a deficiency, discuss it with your doctor.
Does diet affect free carnitine levels?
Dietary changes alone won’t significantly alter free carnitine levels, but certain supplements (like L-carnitine) may influence results. Always follow your provider’s advice regarding diet and supplements.
  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