Because of the enormous technological revolution, the most difficult tasks that humans cannot perform are now easily addressed by small digital gadgets. An example of this technological revolution is Wireless Sensor Networks (WSN). In the WSN, numerous heterogeneous types of sensors work together to sense, monitor, capture, process, and control the physical condition of a specific region or object. The WSN has been used extensively in a number of key areas, particularly in the medical, agricultural, military, and traffic management sectors. The little electronic gadget that forms the WSN is composed of three major components: a sensing component, a power storage component, and a wireless transmission component. Despite the numerous benefits of this modern technology, security remains an unresolved concern. The goal of this work is to develop an efficient Lightweight Secure Key Distribution Protocol (LSKDP) for enhancing the process's safety in heterogeneous medical WSNs. Additionally, security and performance analyses were conducted to demonstrate the suggested methodology's efficacy. The security analysis is performed to ascertain the proposed method's vulnerability to network threats. Additionally, performance analysis is used to determine the CPU utilization, memory consumption, processing power, and computational overhead of the suggested methodology. The experimental results indicate that the suggested strategy detects attacks more accurately and with a lower computational overhead.