With the development of computer and biomedical technologies, medical JPEG images contain the patients’ personal information and the security of the private information attracts great attention. Steganography is utilized to conceal the private information, so as to provide privacy protection of medical images. Most of existing JPEG steganographic schemes embed messages by modifying discrete cosine transform (DCT) coefficients, but the dependencies among DCT coefficients would be disrupted. In this paper, we propose a new medical JPEG image steganographic scheme based on the dependencies of inter-block coefficients. The basic strategy is to preserve the differences among DCT coefficients at the same position in adjacent DCT blocks as much as possible. The cost values are allocated dynamically according to the modifications of inter-block neighbors in the embedding process. Experimental results show that the proposed scheme can cluster the inter-block embedding changes and perform better than the state-of-the-art steganographic method. © 2017 Elsevier Ltd