Telecare Medicine Information Systems (TMIS) improve the medical and healthcare services by information and communication technology. The doctor can monitor the patient's physiological condition by TMIS, the confidentiality of this sensitive data should be protected, which is the key issue in the Health Insurance Portability and Accountability Act. Guo et al. proposed an efficient and provably secure certificateless public key encryption scheme for TMIS. They claimed that their scheme is secure under the random oracle model. Unfortunately, by giving concrete attack, we find that their scheme actually does not reach the security as they claimed. Then we propose an improved scheme to make up for the defect in their scheme.