Internet of Things (IoT)is a fast-growing technology which connects and communicates among things using the internet. Also, generated data are stored as a knowledge base, which helps things to perform automatically without human intervention. IoMT for healthcare applications provides more benefits to patients affected by diseases which required continues health observation. Security issues in IoMT applications cause major problems like allowing an unauthorized person to monitor patient information, treatment procedure, and pharmaceutical detail which makes patients life insecure. Security mechanisms adopted in the general medical devices are may not be suitable for medical IoT because of constrained resource usage such as less energy consumption, less processing power, and less memory usage. In order to secure sensitive data transmission among a lightweight IoMT device communication, this work proposes a new energy optimized lightweight security algorithm. In this work, Modified Simon's (M-Simon) mix column lightweight algorithm is proposed. M-Simon is implemented to reduce the energy consumption of the lightweight medical things using a reduced number of secure round function from 36 to 24 and the sensor data is encrypted with smaller 48-bit key mix column algorithm. Results concluded that the proposed security algorithm reduces higher energy consumption without compromising security in IoMT for healthcare applications. © BEIESP.