Platform
Company
Metabolic Disorders
Review status
Currently under review
Pending specialist review and validation.
This test measures free carnitine, the unesterified form of carnitine, in your blood. Carnitine helps move fatty acids into mitochondria, the parts of cells that turn fat into usable energy. The C0 result reflects the pool of carnitine that is immediately available for this transport function.
Clinicians use free carnitine alongside total carnitine and acylcarnitines to assess how your body uses and transports fat for energy. It is helpful in evaluating suspected inherited carnitine transport problems, monitoring supplementation, and investigating secondary causes of carnitine depletion related to illness, nutrition, kidney function, or certain medicines.
When free carnitine is too low, cells may struggle to use fat efficiently, which can contribute to low energy, muscle weakness, enlarged or weakened heart muscle, and low blood sugar, especially during fasting or illness. Very low values can point to a genetic carnitine transport defect, but they can also occur due to other conditions that reduce intake, increase losses, or raise demand.
This test is often ordered for newborns after an abnormal screen, for children or adults with unexplained fatigue, hypoglycemia, cardiomyopathy, or exercise intolerance, and to monitor carnitine therapy. It can also help identify secondary depletion from nutritional issues, kidney or liver problems, or medications known to lower carnitine. Higher values are most often seen with supplementation or reduced kidney clearance.
Your result is interpreted together with your symptoms, medical history, diet, and related tests such as total carnitine and an acylcarnitine profile. A result below the expected range may prompt repeat testing, assessment of other carnitine measures, urine organic acids, kidney and liver evaluation, and sometimes genetic testing to look for a carnitine transporter defect. In newborns, low values can reflect the baby’s status or the mother’s status, so testing a parent is sometimes recommended.
A result above the expected range is commonly due to carnitine supplements or decreased kidney clearance. If you take levocarnitine, your clinician may ask about dose timing relative to the blood draw. Regardless of the direction of change, one result does not make a diagnosis. Your clinician will discuss next steps, which may include dietary changes, medication review, targeted supplementation, or referral to a metabolic specialist.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Levocarnitine supplements can raise free carnitine levels. Tell your clinician what you take and when you took your last dose before the blood draw.
Valproic acid and pivalate-containing antibiotics can reduce carnitine by increasing losses or utilization. Provide a full medication list, including recent courses.
Newborn values can reflect the mother’s carnitine status and change rapidly after birth. Clinicians may test a parent and repeat the infant test for clarity.
Low intake of animal-based protein, prolonged poor intake, or total parenteral nutrition can reduce carnitine stores. Share details about your typical diet and recent illness.
Kidney problems can cause carnitine loss or reduced clearance, and liver disease can affect synthesis and metabolism. Your provider may review kidney and liver tests.
Recent feeding, acute illness, or sample handling delays can influence results. Follow any fasting or timing instructions and inform the lab about recent illnesses.
References