This study investigated the influence of exercise and fasting state on haematologic and biochemical parameters in juvenile green turtles (Chelonia mydas). Animals were divided into two groups; one group was fasted for 72 h and one group was fed 1 h prior to exercise. Exercise was induced by repeated righting reflexes and blood values were measured prior to and post-exercise. Prior to exercise, fasted animals showed significantly decreased levels of urea, pH, P_VCO₂and HCO₃^-and significant increases in Cl^-and P_VO₂, compared to fed animals and fasted animals had significantly poorer exercise performance. Following exercise both fasted and fed animals had significant increases in Na⁺, K⁺, Cl^-, P_VCO₂, P_VO₂, urea and lactate and significant decreases in pH and HCO₃^-. The magnitude of increase in lactate levels was significantly less in fasted animals. Prior to exercise, a significant correlation was calculated in fasted animals between pH and HCO₃^-. Following exercise, significant correlations were calculated in fed animals between pH and HCO₃^-, P_VCO₂and lactate, and between pH and HCO₃^-in fasted animals. These results show that analytical method, fasting state and the physiologic changes induced during the intense exercise can affect haematologic and biochemical analytes and these factors should be considered when interpreting results from health assessment of wild animals.