This study was designed to investigate the effect of a single dose glucocorticoid administration on the parameters related to energy metabolism in sheep. Forty healthy lactating fat tailed ewes, 2-3 years old, were obtained from the Farm of the University of Kafkas. The animals were divided into control (n=20) and treated group (n=20). Ewes in the treatment group (n=20) was parenterally given a single dose of 0.025 mg/kg dexamethasone (Deksavet %0.4 enj.(R), Interhas, Istanbul-Turkey) at the beginning of the study. Ewes in the control group (n=20) were parenterally given the same dose of placebo at the beginning of the study. All animals were blood sampled before the drug administration and on the 1(st), 2(nd), 3(rd), 4(th), 5(th) and 7(th) day of injection. Sera samples were analysed for the determination of concentrations of insulin, beta-hydroxybutyric acid (BHB), non esterified fatty acid (NEFA), glucose, triglycerides, cholesterol, aspartate aminotransferase (AST), total protein, albumin, globulin and phosphorus. Cholesterol, glucose (P < 0.001) and insulin (P < 0.05) concentration obtained on day 1, 2, 3, 4, 5 and 7 were significantly higher than the baseline values on day 0. Concentrations of cholesterol and glucose peaked on day 7 and 3, respectively. NEFA concentration was significantly lower during the experiment except for day 7 when it peaked (P < 0.05). Other examined parameters did not significantly change when compared to the baseline values. Comparison of the control and the treated group revealed a statistically significant increase in the concentrations of glucose on day 2, 3, and 4, cholesterol on day 3, 4, 5, and 7, insulin on day 1, 2, 3, 4, 5, and 7 while concentrations of NEFA decreased on day 1, 2, 3, 4, and 7 and phosphorus concentrations decreased on day 4.