The use of Internet of Things (IoT) in healthcare systems the world has also measured substantial improvement in patient care by offering real time monitoring and diagnosis. But growing connectivity means that sensitive medical data is also vulnerable to numerous security threats like man-in-the-middle (MITM) attacks, key theft, and device cloning, among many others. These traditional methods for authentication, based on either passwords or static keys, are especially susceptible to such cyber-attacks; thus, they are ineffective in protecting healthcare IoT environments characterized by dynamic threat landscapes. This research article presents a new dynamic key-based authentication scheme for healthcare Internet of Things (IoT) networks. In the suggested framework, mutual authentication between each of the healthcare server and the physical IoT client device is used to protect the sensitive data of the patients in transit, along with providing real-time secure transmission. By focusing on how cryptographic keys develop, the framework addresses current security threats, including key theft and MITM attacks. Not only does this method keep computational and communication costs low; it is also lightweight enough for resource-constrained medical IoT devices using a lightweight authentication protocol. This system is efficient with respect to data size between registration and authentication phases while performing better than all other systems. It also minimizes latency and bandwidth usage by improving the caching layer. The scheme is also computationally cheap, making it feasible in resource-poor healthcare settings. The security analysis tools confirm that the suggested architecture is resistant to ordinary attacks such as MITM and replay attacks while incurring low overhead.