The lack of sensitive and specific markers of inflammation poses a diagnostic challenge in sick or injured reptile patients. The objective of this study was to investigate the diagnostic performance of blood analytes associated with inflammation in healthy (n = 24) and sick (n = 38) gopher tortoises (Gopherus polyphemus). Receiver operating characteristic analysis identified the following as the best-performing diagnostic tests: erythrocyte sedimentation rate (area under the curve [AUC] = 0.812; 95% confidence interval [CI] = 0.693, 0.900), absolute mature heterophils (AUC = 0.771; 95% CI = 0.646, 0.869), total leukocytes (AUC = 0.767; 95% CI = 0.642, 0.866), lactate (AUC = 0.766; 95% CI = 0.641, 0.864), and absolute immature heterophils (AUC = 0.755; 95% CI = 0.628, 0.856). These results support the clinical application of additional tools for the diagnosis and monitoring of inflammatory disease in gopher tortoises. Clinicians may consider adding erythrocyte sedimentation rate and lactate to the minimum database for this species.