Prothrombin time (PT), first used in 1935, is the most commonly employed marker of coagulopathy to assess bleeding tendency. It is a screening test and measures the time in seconds to the formation of a clot after platelet-poor plasma has been mixed with a thromboplastin reagent consisting of tissue factor, lipids and calcium chloride ions. The International Normalized Ratio (INR) is a standardized number based on the PT of the patient. It is used by clinicians to measure the effectiveness of anticoagulants and to guide therapy. Drugs such as warfarin can affect the level of or the metabolism of vitamin K in the body, which can impact PT and INR levels. A supratherapeutic INR is rare in a patient not on therapy with vitamin K inhibitors and with preserved liver function. Here we describe an elderly man with a supratherapeutic INR, secondary to the use of rifampin. Antibiotic-induced coagulopathy is an extremely rare complication. To the authors' knowledge, this is a unique case of rifampin-induced coagulopathy with no other associated complications of disseminated intravascular coagulation. A literature review revealed a small number of cases of rifampicin-induced coagulopathy. A high index of suspicion and knowledge is essential for the diagnosis and management of such cases.