Electronic Medical Records (EMRs) contain private and sensitive information of the patients and require distribution across multiple stakeholders for sustained and consistent medical care. EMRs are owned and maintained by hospital systems. So, patients often face difficulties in getting their data shared among different stakeholders. Blockchain provides distributed, transparent, and immutable log of records that benefit the design of healthcare systems. There have been several studies done to use Blockchain technology as a mediation tool for sharing sensitive EMRs between multiple stakeholders in the e-health care system. However, these studies lack the requirement of patients to have full control over their EMR data. This work develops PACEX, PAtient-Centric EMR eXchange, that enables patients to share and have complete control over their data using Blockchain. In PACEX, we develop an easy-to-use patient application that interacts with different hospital systems and handles EMR exchanges with integrity. We developed a proof of concept implementation of PACEX using Ethereum Blockchain and Smart Contracts to achieve access control and maintain a history of record exchanges among different stakeholders. The evaluation results provide the quantitative analysis that gives time estimates for various transactions involved in PACEX and the qualitative analysis that describes the security properties of the system. PACEX achieves essential security requirements such as Authentication, Integrity, Access Control, and Traceability over the EMR data exchange. © 2019 IEEE.