PURPOSE: Thromboelastography (TEG) has been recommended to characterize post-traumatic coagulopathy, yet no study has evaluated the impact of pre-injury anticoagulation (AC) on TEG variables. We hypothesized patients on pre-injury AC have a greater incidence of coagulopathy on TEG compared to those without AC. METHODS: This retrospective chart review evaluated all trauma patients admitted to an urban, level one trauma center from February 2011 to September 2014 who received a TEG within the first 24h. Patients were classified as receiving pre-injury AC or no AC if their documented medications prior to admission included warfarin, dabigatran, or anti-Xa (aXa) inhibitors (apixaban or rivaroxaban). The presence of coagulopathy on TEG or conventional assays was defined by exceeding local laboratory reference standards. RESULTS: A total of 54 patients were included (AC, n=27 [warfarin n=13, dabigatran n=6, aXa inhibitor n=8] vs. no AC, n=27). Baseline characteristics were similar between groups, including age (72±13years vs. 72±15; p=0.85), male gender (70% vs. 74%; p=0.76) and blunt mechanism of injury (100% vs. 100%; p=1). There was no difference in the number of patients determined to have coagulopathy on TEG (no AC 11% vs. AC 15%; p=0.99). Conventional tests, including the international normalized ratio (INR) and activated partial thromboplastin time (aPTT), identified coagulopathy in a high proportion of anti-coagulated patients (no AC 22% vs. AC 85%; p<0.01). CONCLUSION: TEG has limited clinical utility to evaluate the presence of pre-injury AC. Traditional markers of drug induced coagulopathy should guide reversal decisions.