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 health searches conducted in Germany and found that 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. By comparison, Germany’s public broadcaster NDR and established medical reference sites such as MSD Manuals were cited far less frequently.
The researchers warned that YouTube is not a medical publisher and allows content from anyone, including creators with no medical training, meaning popularity may outweigh medical authority. AI Overviews appeared in more than 82% of the health searches analysed.
Google said its system is designed to surface high-quality information regardless of format and argued that much YouTube content cited comes from hospitals, clinics and licensed professionals. However, the study noted that highly credible videos made up less than 1% of all YouTube links cited in health-related AI summaries.
Independent experts said the findings suggest the risks of misinformation are structural rather than rare, with AI Overviews prioritising visibility and engagement over medical reliability.
