<p>The advancement of cloud-assisted Internet of Medical Things (IoMT) technology brings about the storage and transmission of large volumes of data, including sensitive user information that necessitates careful protection. As a result, ensuring data accessibility and privacy poses a significant challenge in IoMT development. Proxy re-encryption technology presents an effective solution for privacy protection. However, existing schemes often suffer from limitations such as insufficient fine-grained access control and high computational overhead, which hinder their practical deployment in resource-constrained IoMT environments. Moreover, data owners frequently lose control over data once re-encryption keys are issued, increasing the risk of unauthorized access and key misuse. To tackle these challenges, we propose an outsourcable hybrid proxy re-encryption scheme that integrates the conventional public key cryptosystem with the attribute-based cryptosystem, supporting outsourcing decryption for flexible and efficient data sharing in IoMT. We demonstrate the scheme’s ciphertext indistinguishability under adaptive chosen ciphertext attack (CCA security), proving its superior security compared to similar schemes. Furthermore, our scheme empowers data owners with control over the generation of re-encryption keys, ensuring complete data management rights. Simulation results on the eICU collaborative research database, using the JPBC library, validate the feasibility of our proposed scheme. The results indicate that our scheme’s computational cost is significantly lower than that of comparable schemes.</p>