Magnesium participates in numerous enzymatic reactions in the human body and it has an essential role in maintaining the antioxidant system. Our purpose was to investigate the effect of magnesium on element content in blood. Male Wistar rats were divided into four groups. The animals in group I. were fed with normal diet, the animals in group II. were fed with normal diet and treated with magnesium polygalacturonate (200 mg Mg/kg body weight ad libitum daily). The animals in group III. were fed with fat rich diet containing cholesterol (2.0%), sunflower oil (20%) and cholic acid (0.5%) added to the control diet. The animals of group IV. were fed with fat-rich diet and magnesium polygalacturonate. The rats were kept on the diets for 9 days. The element concentration (Al, As, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Ni, P, Pb, S, Si, Sn, Sr, Ti, V, Zn) of blood samples was determined with an ICP-OES after digestion with a mixture of nitric acid and hydrogen peroxide. The results show that the concentration of several elements changed significantly in both magnesiumtreated groups, nevertheless the alteration was different in the control and hyperlipidemic groups. It has been concluded that high amount of magnesium supplementation alters the metal ion homeostasis in short-term experiment. Although some favourable effects were found in the hyperlipidemic group by magnesium polygalacturonate treatment, it is worth to note that supplementation with magnesium should be carried out carefully especially in metabolic diseases.