BACKGROUND Obesity is known as a major risk factor for postoperative vein thrombosis. Thromboelastography (TEG) is used to monitor viscoelastic features of blood clots. The aim of this study was to determine hypercoagulable states in patients undergoing bariatric surgery and to assess dynamics of coagulation parameters in the perioperative setting using TEG. MATERIAL AND METHODS We included 60 consecutive patients undergoing bariatric surgery. TEG alterations were assessed at 4 time points: at baseline, after the surgery, and on postoperative day 1 (POD1) and 2 (POD2). Hypercoagulable state was defined when patients showed clot strength (G) of ≥11 dynes/cm² or maximum amplitude (MA) ≥68 mm. RESULTS Fourteen patients (23.3%) out of 60 showed hypercoagulability prior to surgery on TEG. Fibrinogen levels were significantly higher in the G ≥11 group compared to the G <11 group, at 4.2 and 3.8 g/l, respectively (p=0.02). Seventeen patients (28.3%) had MA ≥68 mm at baseline. Fibrinogen levels increased significantly from 3.90 at baseline to 4.16 g/l in POD2 (p<0.001). There was an increase in mean reaction time from baseline (6.74 s) to POD2 (7.43 s, p=0.022). We found a correlation between baseline fibrinogen levels and MA (R=0.431, p=0.001) or G (R=0.387, p=0.003). ROC curve analysis showed that fibrinogen levels can predict clot strength (G) ≥11 dynes/cm² with AUC=0.680 (p=0.044). CONCLUSIONS A considerable proportion of patients referred to bariatric surgery show a trend towards hypercoagulability on TEG. This study shows the potential of hypercoagulation monitoring by TEG in the perioperative setting of bariatric surgery.