ELISABETA ANTONESCU, GABRIELA BOTA, BOGDAN SERB, DITER ATASIE, CRISTINA DAHM TATARU, MARIA TOTAN, LAVINIA DUICA, SINZIANA CALINA SILISTEANU, JULIANNA SZAKACS, OANA CRISTINA ARGHIR, IOAN OSWALD, MARINELA MINODORA MANEA STUDY OF THE TOTAL SERUM CONCENTRATION OF SERRUM IONIZED MAGNESIUM IN CHILDREN AND ADOLESCENTS FROM SIBIU AREA Magnesium is an essential nutrient for the living organisms and plays an important part in the prevention and treatment of many diseases. It is an enzymatic cofactor for more than 300 reactions. Magnesium is essential for regulating blood pressure, muscle contraction, cardiac excitability, insulin metabolism, vasomotor tonus. Studying the way in which serum magnesium concentration varies in children and adolescents in the Sibiu area according to the reference intervals we especially set for this area. The study is a retrospective one, using approximately 4900 data from the archives of the Medical Analysis Laboratory within the Sibiu Pediatric Clinical Hospital. Serum magnesium was dosed using the Konelab Prime 30i analyser. The data from the literature was used to compare the results. The reference ranges obtained in the current study were similar to the literature studied. The percentage of patients with magnesium concentration outside the reference ranges was roughly equal for all age groups. The difference was between 1 month and 2 year-old children with very few deviations from the reference range. The results of our study reflect more accurately the real reference range for the population in the Sibiu area, helping clinicians to establish a diagnosis as quickly and accurate as possible. These results were not significantly different from the literature studied.