In telemedicine, the protection of exchanged medical data, particularly images, is essential to guarantee the confidentiality and integrity of sensitive information. The aim of this work is to develop a watermarking method that ensures the security of these data while preserving their visual quality. We propose a two-stage approach, in the first step, a text watermark containing sensitive information is embedded in a grayscale image using a combination of the Discrete Cosine Transform (DCT) and the K-means algorithm. In the second step, this watermarked image is embedded in a color medical image using the Discrete Wavelet Transform (DWT) and the Self-Organizing Map (SOM) algorithm, with Reed-Solomon (RS) coding to enhance security. Experimental results show that our method achieves high imperceptibility, with a peak signal-to-noise ratio (PSNR) of 45 dB. In terms of robustness, our approach effectively resists various attacks, displaying a normalized cross correlation coefficient (NCC) close to 1 for several types of attack. Statistically, our method achieves a 5-10 % higher PSNR compared to state-of-the-art techniques and maintains an NCC above 0.99 under noise, compression, and filtering attacks, outperforming existing methods by 8–15 % in robustness metrics.