With the growth in population, there is an increase in the amount of Electronic Health Records (EHR) and so is the rise in concern regarding their security and privacy. At present, the security and privacy of EHR have gained significant importance. This research paper gives an indebt understanding of what EHR comprises and why they need to be secured. Further how the Internet of Medical Things (IoMT) devices contribute towards adding records into these EHR. Further, this paper answers Why these EHR are saved as big data? This research also compares the already prevalent security technique used in EHR. Finally, this paper studies the various performance evaluation metrics which are commonly used for the evaluation of EHR.