Google’s AI Overviews, which generate summaries at the top of search results and are seen by about 2 billion users each month, cite YouTube more often than any medical website when answering health-related queries, according to new research.
The study, conducted by the SEO platform SE Ranking, analysed responses to more than 50,000 healthcare-related searches made in Germany. It found that YouTube accounted for 4.43% of all citations used by AI Overviews, making it the single most referenced source. No hospital network, government health authority or academic medical institution came close to that level of citation.
Researchers warned this was significant because YouTube is not a medical publisher and hosts content from a wide range of creators, including non-medical influencers. While some videos are produced by hospitals or licensed professionals, many are not.
Google said AI Overviews are designed to surface high-quality, reputable information in different formats and argued that much of the YouTube content cited comes from credible medical sources. It also noted the study was limited to German-language searches in Germany and may not reflect results elsewhere.
The findings come amid growing scrutiny of AI Overviews after previous investigations found misleading and potentially harmful medical information appearing in summaries. In this study, AI Overviews appeared in more than 82% of health-related searches.
Among the most cited sources after YouTube were German public broadcaster NDR, followed by medical reference sites and consumer health portals. Experts say the results suggest AI Overviews prioritise visibility and popularity over medical authority, raising concerns about the structural risks of relying on generative AI for health information.
