Blood draw
Carnitine Differentiation
Carnitine fraction profile; fatty acid metabolism.
€ 116,00
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Vitamins, minerals and amino acids · Blood
Carnitine, free
The part of carnitine that is still freely available to bring fatty acids into the cell.
At a glance
- Measured in blood
- In 1 test panel
- No special preparation
Explanation
Carnitine, free: what is measured?
Carnitine carries long fatty acids to the mitochondria, the tiny energy factories of the cell. As soon as carnitine picks up a fatty acid, it is called acylcarnitine. Free carnitine is the part that has not bound anything yet and is therefore available for transport. The body makes carnitine itself in the liver and kidneys; it also comes from meat and dairy. Together with the bound part, free carnitine makes up the total carnitine.
What can it detect?
- A shortage of available carnitine, for example with kidney dialysis or with certain medicines
- Rarely: an inherited disorder of carnitine transport or fatty acid breakdown, which usually causes symptoms in childhood
Result
What does the result mean?
Carnitine, free too high
A high value is usually caused by a carnitine supplement or a meat-rich diet; reduced kidney function can also raise the value. No symptoms are known to go with a high value. A high value does not mean that the body burns more fat or makes more energy.
Carnitine, free too low
A low free carnitine can mean two things. There may be too little carnitine overall, for example due to low intake, dialysis, severe malnutrition or long-term use of valproic acid or certain antibiotics. Or there is enough carnitine, but much of it is bound to fatty acid residues, for example with a disorder of fatty acid breakdown or during prolonged fasting. That is why free carnitine is always looked at together with acylcarnitine. Symptoms of a true shortage include muscle weakness, heart problems and low blood sugar when ill or fasting.
After an abnormal result
With a low value, the GP assesses the result together with total carnitine, acylcarnitine, kidney function, diet and medicine use. With a clearly low value without an explanation, or with muscle, heart or blood sugar symptoms, referral to an internist (specialist in internal medicine) or a specialized center for metabolic diseases follows.
Reliability
How reliable is the test?
For adults without symptoms, the meaning of an abnormal value has been little studied. Free carnitine can only be interpreted together with total carnitine and the acylcarnitine profile; only that combination shows whether there is too little carnitine or whether it is mainly bound. The value also varies with diet and with how long someone has been fasting. In the Netherlands, inherited disorders of fatty acid breakdown are detected through the newborn heel prick screening.
What can affect the result?
- Longer fasting or being ill lowers free carnitine, because more of it is then bound to fatty acids; the time of sample collection and the last meal affect the result.
- A supplement or a meat-rich diet raises the value; a vegetarian or vegan diet lowers it without there being a disease.
- Reduced kidney function raises the value, dialysis lowers it sharply.
- Measurement methods and reference values differ between laboratories and are not standardized.
Who it is for
Who is the test useful for?
Useful for
The result is mainly meaningful when a metabolic disease is suspected, with kidney dialysis and with long-term use of medicines that lower carnitine. In adults without symptoms, the value on its own adds little, and without the acylcarnitine it cannot be properly interpreted.
How common is it?
Inherited disorders of carnitine transport or fatty acid breakdown are rare. In the Netherlands, on average 15 to 20 children with MCADD are born each year and about 1 child with CPT1 every five years; both are detected through the heel prick. There are no Dutch figures on how often a low free carnitine occurs in adults.
RIVM, prenatal and neonatal screening (heel prick)
Drawbacks and risks
- A low free carnitine due to fasting or diet can wrongly be read as a disease.
- Without the acylcarnitine, a disorder of fatty acid breakdown can be missed or, on the contrary, wrongly suspected.
Get tested
Carnitine, free: test panels
Carnitine, free is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.
Evidence
Sources
This explanation is based on Dutch guidelines and independent information. It is general information, not a diagnosis. Discuss an abnormal result with your GP.
More about risks and resultsMore explanations
Other tests: Vitamins, minerals and amino acids
- AC/FC ratio
- Acylcarnitine
- Alanine
- Antibodies against intrinsic factor
- Arginine
- Calcium
- Calcium (albumin-corrected)
- Carnitine, total
- Coenzyme Q10
- Copper
- Folic acid
- Glutamic acid (urine)