Introduction: In the context of a shrinking healthcare budget, poor physician cost awareness, and continued over-utilization of low-value tests in the emergency department, we re-designed our computerized order entry system to reduce the use of coagulation testing. Methods: A hospital-based prospective pre-post analysis following de-bundling of INRPTT testing in two academic hospital emergency departments (annual visits 140,000). All participants aged 18 years or older undergoing evaluation and/or treatment at either of during the period of August 1, 2015 to July 24, 2016 were included. Primary outcome is coagulation testing utilization rates and associated costs. Results: Unbundling INR and aPTT testing resulted in significantly decreased bundled INRPTT testing relative to baseline (INRPTT tests per patient per day: 0.60 [95% CI: 0.57-0.62] vs. 0.98 [95% CI: 0.98-0.99], p=0.000), with significantly increased targeted testing (INR tests per patient per day: 0.39 [95% CI: 0.37-0.42] vs. 0.00 [95% CI: 0.00-0.01], p=0.000; PTT tests per patient per day: 0.33 [95% CI: 0.30-0.36] vs. 0.01 [95% CI: 0.00-0.01], p=0.000). As a result of unbundling, there was a significant decrease in costs associated with coagulation testing relative to baseline (Cost per day: $958.52 [INRPTT $592.78+INR $183.91+PTT $181.83] vs. $1,074.50 [INRPTT $1,069.76+INR $2.06+PTT $2.68], p=0.000), realizing estimated daily and yearly savings of $115.98 and $42,332.70, respectively. Conclusion: Compared to baseline practice patterns, unbundling coagulation testing resulted in the reduction of coagulation testing suggesting system design and user workflows to be an integral factor to provider practice patterns. Given the significant cost-savings, we recommend institutions carefully re-evaluate their system design and user workflows to optimize emergency department laboratory utilization.