Google’s AI Overviews feature most often cites YouTube when answering health-related search queries, according to a new study that raises concerns about the reliability of information shown to billions of users.
Researchers at SE Ranking analysed more than 50,000 health queries 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. The next most cited sources included Germany’s public broadcaster NDR and medical reference sites such as MSD Manuals and NetDoktor.
The researchers warned that YouTube is not a medical publisher and hosts content from a wide range of creators, including influencers with no medical training. They argued this reliance risks prioritising popularity and visibility over medical accuracy, even in a country with a tightly regulated healthcare system.
AI Overviews appeared in more than 82% of the health searches studied. While Google says its summaries are designed to highlight high-quality information from reputable sources, critics note that the platform has previously produced misleading or incorrect medical advice, prompting Google to remove AI Overviews from some health queries.
Google responded that many highly cited YouTube videos come from hospitals, clinics and licensed professionals, but the researchers countered that these represented less than 1% of all YouTube links used in AI Overviews. Experts say the findings suggest the risks of misinformation are structural, not isolated, and call for stronger safeguards when AI systems summarise health information.
