Free Carnitine in Serum (or Plasma)
This test measures the amount of free carnitine, a key molecule that helps transport fatty acids into cells for energy production.
["Free carnitine helps assess how well your body is using fats for energy and may indicate metabolic or muscle disorders."]
Key facts at a glance
- LOINC
- 48430-3
- Short code
- CARN-SM
- Synonyms
- Carnitine ?Tm sub Smn Qn
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, wide-mouth, leak-proof semen collection container (non-toxic plastic, preferably polypropylene)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- male
- Age range
- ≥ 18 years
- Method
- Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
- CPT
- 82379
- SNOMED
- 44608005
- Specimen volume
- Entire ejaculate (typically 1.5-5 mL)
- Stability
- Seminal plasma should be separated by centrifugation within 1 hour of collection. Separated seminal plasma is stable for 24 hours at 2-8°C; for longer storage, freeze at -20°C or below. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 48–168 hours
- Order
- routine
Why This Test Might Be Ordered
Your doctor may recommend this test if you have symptoms like muscle weakness, fatigue, or unexplained metabolic issues. It’s also used in diagnosing conditions like carnitine deficiency, mitochondrial disorders, or certain genetic metabolic diseases. Sometimes it’s part of a broader evaluation for unexplained muscle pain or liver problems.
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 draw if your doctor specifies it. Bring any medications you’re taking, as some may affect results. Avoid strenuous activity or excessive exercise 24 hours before testing.
What Happens During the Test
A healthcare provider will collect a blood sample from a vein in your arm. You may feel a slight pinch, but it’s quick and shouldn’t cause discomfort. The sample is sent to a lab for analysis using a specialized method to measure free carnitine levels.
What the Results Mean
Results are compared to a reference range specific to your lab. Low levels may suggest carnitine deficiency, mitochondrial disorders, or certain genetic conditions. High levels could indicate liver disease, kidney problems, or other metabolic issues. Your doctor will discuss these findings in the context of your symptoms and medical history.
Reference range
Reference ranges for carnitine in semen are not well-established; clinical correlation is recommended. Consult laboratory-specific reference values.N/A
No special patient preparation required. Patient should abstain from ejaculation for 2-5 days prior to specimen collection for optimal semen quality.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
Free Carnitine
Frequently asked questions
How often do I need this test?
Can diet affect my results?
What if my results are outside the normal range?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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