This paper proposes a novel medical image encryption method based on fast and robust fuzzy C-means clustering image segmentation method and deoxyribonucleic acid encoding. Firstly, the plain medical image is split to interested pixels and uninterested pixels, respectively. Then, the uninterested 0-value pixels are abandoned to reduce the pixels in encryption. Secondly, for the interested pixels, some low-value pixels are also discarded by image segmentation to further reduce the encryption time. Thirdly, a 4-dimensional hyperchaotic system is utilized to process the main pixels of medical image with deoxyribonucleic acid encoding. Finally, lossless encryption and fast encryption are done for different purposes and security analysis shows that the encryption method is robust and secure to resist various attacks.