Background Juvenile idiopathic arthritis (JIA) is not a single disease; it9s group of all arthritis with unknown etiology, starting before 16 years of age and lasting at least 6 weeks long. JIA is the most common rheumatic disease in childhood. Carnitine is an important molecule in cellular energy metabolism. Secondary carnitine deficiency can be detected in chronic diseases by either renal loss or increased demand. Objectives We hypothesized that secondary carnitine deficiency may be seen to increased demand in JIA patients. In the present study our aim is to determine free carnitine and acyl-carnitine levels of Turkish JIA patients. Methods 114 patients with a diagnosis of juvenile idiopathic arthritis and a healthy 50 individuals served as control group, were included to the study. A fasting blood sample was taken for free carnitine and acyl-carnitine esters with tandem mass spectrometry from children in both groups. Results Screening of acyl-carnitine profile revealed free carnitine, C14, C16, C16-OH, C18 and C18:2-OH carnitine levels were higher (p Conclusions In the present study we were not able to define secondary carnitine deficiency in JIA patients, therefore routine carnitine supplementation is not recommended in all patients with JIA. References Ravelli A, Martini A. Juvenile idiopathic arthritis. Lancet. 2007 Mar 3; 369(9563):767-78. Stanley CA. Carnitine deficiency disorders in children. Ann N Y Acad. Sci.2004; 1033:42–51. Disclosure of Interest None declared