OBJECTIVE The use of an off-label dose of four-factor prothrombin complex concentrate (PCC) for International Normalized Ratio (INR) reversal in a patient before a diagnostic lumbar puncture is reported. CONCLUSIONS A 57-year-old, 122-kg man arrived at the hospital with a possible diagnosis of meningitis and had an INR of >3 while on warfarin therapy. The patient initiated warfarin therapy in 2009 due to recurrent deep vein thrombosis. The patient required reversal of his elevated INR in order for a lumbar puncture to be safely performed (INR must be no higher than 1.4). Multiple units of fresh frozen plasma (FFP) were administered, with a subsequent INR decrease to 1.9. Additional units of FFP were given. The patient developed respiratory decompensation due to volume overload, partially caused by the administration of multiple units of FFP. As the INR remained above 1.4 but was less than 2, an alternative dosing strategy was used. A dose of 1020 units of factor IX, equaling about 10 mg/kg based on a maximum dosing weight of 100 kg, was administered. The two vials of PCC administered each contained 510 units of factor IX. No vitamin K was given. The patient's INR, checked 30 minutes after PCC administration, was 1.3, and the lumbar puncture was performed. The lumbar puncture was completed without complication, and the patient was restarted on therapeutic anticoagulation the following day. CONCLUSIONS A 57-year-old patient was successfully treated with low-dose PCC to reverse an INR from 1.7 to 1.3 in order to perform a diagnostic lumbar puncture.