Carnitine - plasma or serum

Last updated: Thursday, 08, April, 2004

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Item Process

5 mL blood in lithium heparin or plain tube.


Radiometric, spectrophotometric assay.

Reference Interval

Free: 30-70 µmol/L

Total: 40-80 µmol/L


Investigation of carnitine-deficient states, either primary (due to decreased intake, impaired synthesis or impaired renal reabsorption) or secondary (due to organic acidaemias).

Severe carnitine deficiency may be associated with hypoglycaemia, myopathy or cardiomyopathy.


Hypoglycaemia, muscle weakness and cardiomyopathy do not occur until the level is less than 10 µmol/L.

In carnitine deficiency secondary to organic acidaemias, there is a relatively greater reduction in free carnitine.


Engel AG and Rebouche CJ. J Inher Metab Dis 1984; 7: 38-43