A study of Google’s AI Overviews has found that YouTube is the most frequently cited source for health-related search answers, raising concerns about how medical information is prioritised in a tool seen by about 2 billion users each month.
Researchers at SE Ranking analysed more than 50,000 German-language health queries and found that AI Overviews appeared in over 82% of searches. Of nearly 466,000 citations, YouTube accounted for 4.43%—more than any hospital network, government health body or medical association. The next most cited sources were German public broadcaster NDR and medical reference site MSD Manuals.
The researchers warned that YouTube is not a medical publisher and hosts content from both qualified professionals and untrained influencers, meaning popularity may outweigh medical authority. The findings follow previous reporting by The Guardian highlighting cases where Google’s AI summaries gave misleading health advice.
Google said AI Overviews are designed to surface high-quality content in various formats and argued that many cited YouTube videos come from reputable medical channels. However, the study noted that the most reliable videos made up less than 1% of all YouTube links cited.
Hannah van Kolfschooten of the University of Basel said the results suggest the risks of AI-generated health information are “structural, not anecdotal”, with visibility and engagement appearing to drive citations more than medical reliability.
