In the present study, biochemical toxic effects ol oxytetracyciine, widely using in veterinary medicine, on metabolisms of Ca, IP, Mg and vitamin D were investigated. Clinical and laboratory parameters were observed at recommended dose and time period. In this study, healthy 6 dogs (different age and sex) were used as materials. Oxytetracyciine (Primamycine-Pfizer®) was injected (20 mg/kg IM, one a day) to all dogs during 14 days. In 14th day of experiment, it was observed that statistically significant (p<0.01) decrease at concentrations of ICa and adjusted Ca, no significant increase (p>0.0S) at serum levels ot PTH, IP and Mg, and no significant decrease (p>0.05) at serum level of vitamin D. As a result, oxytetracyciine may change metabolisms of Ca, Mg, P and vitamin D. therefore it must be considered that metabolisms of Ca, Mg, P and vitamin D during long term oxytetracyciine treatment.