Google’s AI Overviews cite YouTube more often than any medical website when answering health-related search queries, according to a new German 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 health queries made in Germany and found that YouTube accounted for 4.43% of all sources cited by AI Overviews, more than hospitals, government health portals or academic institutions. The next most cited sources were German public broadcaster NDR and the 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 visibility and popularity may outweigh medical authority. AI Overviews appeared in more than 82% of health searches analysed.
Google said its AI summaries are designed to surface high-quality content in different formats and argued the findings cannot be generalised beyond Germany. It added that most highly cited YouTube videos came from medical channels, though researchers noted these represented less than 1% of all YouTube links used.
Independent experts said the study suggests risks in AI-generated health advice are structural, not isolated, and reflect how the system prioritises sources rather than rare errors.
