BACKGROUND Fulminant hepatic failure (FHF) is commonly associated with elevated prothrombin time (PT) and international normalized ratio (INR). There is a commensurate decline in pro- and anti-hemostatic factors, and hemostatic function is rebalanced, not reflected in INR. This report presents the case of a 36-year-old woman with FHF following acetaminophen overdose, an increased INR above 8.7, and normal blood viscosity measured by rotational thromboelastometry (ROTEM). CASE REPORT A 36-year-old woman presented with FHF following an acetaminophen overdose. On arrival, she was lethargic but arousable and followed commands. Her King's College Criteria for acetaminophen toxicity was 2 and her MELD score was 36. Her INR was unmeasurably high (>8.7). To evaluate whole-blood coagulation, a ROTEM analysis was performed. All parameters (CT, CFT, alpha-angle, A10, MCF) of the NATEM were within reference range. Despite the normal ROTEM, spontaneous bleeding was a concern. The patient received 5 units of cryoprecipitate and 9 units of FFP prior to a central venous line placement. She was started on molecular adsorbent recirculating system and continuous veno-venous hemodialysis, but died on day 7. CONCLUSIONS Patients with FHF can have normal whole-blood coagulation based on ROTEM even if INR levels are unmeasurably high. Viscoelastic tests such as ROTEM, which assesses whole-blood coagulation properties, are preferrable for coagulation monitoring in these patients. Blood product transfusion to correct coagulation abnormality, like FFP and cryoprecipitate, may be used based on the result of viscoelastic testing over conventional coagulation testing.