Google’s AI Overviews cite YouTube more often than any medical website when answering health-related search queries, according to a new study that raises concerns about the reliability of information seen by billions of users each month.
Researchers at SE Ranking analysed more than 50,000 German-language health searches and found YouTube accounted for 4.43% of all sources cited in AI Overviews, making it the single most referenced domain. No hospital network, government health authority or academic medical institution came close. The next most cited sources were a German public broadcaster and established medical reference sites, but at significantly lower rates.
The findings are controversial because YouTube is not a medical publisher and hosts content from a wide range of creators, including influencers with no medical training. Critics argue this suggests Google’s AI may prioritise popularity and visibility over medical authority when generating health summaries.
Google said the study was limited to Germany and that AI Overviews are designed to surface high-quality content across formats, including videos made by licensed professionals. The company added that many highly cited YouTube videos came from hospitals or medical organisations.
Independent experts said the research suggests the risks of misleading health information are structural rather than isolated. While some cited videos are credible, researchers warned they represent only a small fraction of YouTube links used by AI Overviews, leaving open the possibility that less reliable content plays a significant role.
