Health information retrieval and YouTube can be used as powerful tools to improve user's health knowledge. However, YouTube videos must be carefully analysed in order to avoid misleading, inaccurate, obsolete and incorrect health content. We present an approach for re-ranking health videos obtained from YouTube, called Domain-based ranking. Our system automatically identifies videos coming from trusted sources (channels), such as hospitals and health organizations, and re-ranks YouTube results so that such videos are presented first in the ranking list. Video and channel metadata are used to automatically determine if a video is provided by a trusted source. The approach is tested and results show that the amount of relevant and reliable videos ranked within top-10 increase when using Domain-based ranking, compared with the original YouTube ranking.