The purpose of this study was to investigate whether any correlation exists between INR level at discharge and postoperative complications or readmission rates. From 2010–2011, INR levels on discharge, complications and readmissions within 30 days were recorded on 441 patients undergoing joint arthroplasty. Eighty percent (352 of 441) patients had a subtherapeutic INR level at discharge. The overall complication rate was 15% with an 8.6% readmission rate. A supratherapeutic INR level at discharge was associated with both higher readmission rate as well as increased number of complications (P<0.048). Most patients taking warfarin are nontherapeutic at the time of discharge; notably, a supratherapeutic INR places patients at risk for increased complications and readmissions rates following surgery.