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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
38481-8
Short code
C0
Synonyms
Carnitine Free DBS-sCnc
Category
chemistry
Sample
serum
Container
Dried blood spot (DBS) collection card - Whatman 903 filter paper or equivalent
Units
N/A
Ref low
17
Ref high
88
Critical range
10 N/A – 150 N/A
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
Tandem Mass Spectrometry (MS/MS)
CPT
82017
SNOMED
384781004
Specimen volume
Approximately 75-100 µL whole blood applied to filter paper (minimum 3 fully filled blood spots)
Stability
Dried blood spots stable for 7 days at room temperature, 30 days at 2-8°C, and up to 1 year at -20°C. Transport at ambient temperature with desiccant.
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
24–72 hours
Order
routine

Why Is This Test Done?

Your healthcare provider may order a free carnitine test to evaluate metabolic disorders, such as carnitine deficiency, which can occur due to genetic conditions, certain medications, or liver/kidney problems. It may also be used to monitor treatment for conditions like mitochondrial disorders or to check for improper fat metabolism.

What Does a Low or High Level Mean?

Low levels of free carnitine might suggest a deficiency, which can affect energy production and may be linked to muscle weakness, fatigue, or neurological issues. High levels could indicate metabolic stress, such as severe illness, kidney disease, or certain medications. However, results alone don’t diagnose a condition—they’re part of a broader evaluation.

How Is This Test Performed?

A blood sample is drawn from a vein in your arm. The sample is sent to a lab, where free carnitine is measured using a specialized biochemical method. No special preparation is usually needed, but you may be asked to fast or avoid certain foods for a set period before testing.

What Are Common Causes of Abnormal Results?

Abnormal free carnitine levels can result from genetic disorders (e.g., primary carnitine deficiency), liver or kidney disease, certain medications (like antibiotics or anticonvulsants), or conditions affecting fat metabolism. Chronic illness, malnutrition, or excessive exercise may also play a role.

Reference range

Reference ranges vary by age. Typically: 0-7 days: 17-55 µmol/L; 8-30 days: 18-65 µmol/L; 1-6 months: 20-70 µmol/L; 7-12 months: 22-77 µmol/L; 1-3 years: 24-80 µmol/L; 4-6 years: 25-83 µmol/L; 7-10 years: 26-84 µmol/L; 11-17 years: 28-86 µmol/L; Adults: 30-88 µmol/L (per DBS reference intervals)N/A

Specimen: serum

No special patient preparation required. Sample collection recommended prior to next dose for patients on carnitine supplementation. Avoid vigorous exercise immediately prior to collection.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Free Carnitine

Frequently asked questions

What symptoms might lead to this test?
Symptoms like muscle weakness, fatigue, poor growth in children, or neurological issues (e.g., numbness, confusion) may prompt a free carnitine test, especially if other tests or conditions suggest metabolic dysfunction.
How often is this test repeated?
If abnormal, your provider may repeat the test to monitor changes over time, especially if treatment is being adjusted or if symptoms persist. Frequency depends on your condition and response to care.
Can lifestyle changes affect free carnitine levels?
Yes, diet, exercise, and certain medications can influence carnitine levels. For example, high-protein diets or supplements may temporarily alter results. Always discuss lifestyle changes with your healthcare provider before making adjustments.
  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