Google’s AI Overviews cite YouTube more often than any medical website when answering health-related search queries, according to new research that has raised concerns about the reliability of information seen by billions of users each month.
The study, conducted by researchers at SE Ranking, analysed responses to more than 50,000 health queries made in Germany. It found that YouTube accounted for 4.43% of all sources cited by AI Overviews, making it the single most referenced domain. No hospital network, government health body or academic institution came close. YouTube is owned by Google.
By comparison, the next most cited sources were Germany’s public broadcaster NDR, the medical reference site Msdmanuals, and consumer health portal Netdoktor. Official health authorities and hospitals featured far less prominently.
The findings challenge Google’s claims that AI Overviews prioritise authoritative sources such as the Centers for Disease Control and Prevention and the Mayo Clinic. Researchers warned that YouTube is not a medical publisher and hosts content from a wide range of creators, including non-experts, making quality and accuracy inconsistent.
Google responded that many YouTube videos cited by AI Overviews are produced by licensed medical professionals and reputable institutions, and said the results could not be generalised beyond Germany. However, independent experts said the study suggests the risks posed by AI-generated health summaries are systemic, with popularity and visibility appearing to outweigh medical authority in how sources are selected.
