The healthcare industry makes rampant strides in sharing electronic health records with upgraded efficiency and delivery. Electronic health records comprise personal and sensitive information of patients that are confidential. The current security mechanism in cloud computing to store and share electronic health records results in data breaches. In the recent era, blockchain is introduced in storing and accessing electronic health records. Blockchain is utilized for numerous applications in the healthcare industry, such as remote patient tracking, biomedical research, collaborative decision making and patient-centric data sharing with multiple healthcare providers. In all circumstances, blockchain guarantees immutability, data privacy, data integrity, transparency, interoperability, and user privacy that are strictly required to access electronic health records. This review paper provides a systematic study of the security of blockchain-based electronic health records. Moreover, based on thematic content analysis of various research literature, this paper provides open challenges in the blockchain-based electronic health record.