Google’s AI Overviews feature most often cites YouTube when answering health-related search queries, according to a new study that has raised concerns about the reliability of information shown to 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, more than any hospital, government health body or medical association. The next most cited sources were German public broadcaster NDR and the medical reference site Msdmanuals.
The researchers warned that YouTube is not a medical publisher and hosts content from a wide range of creators, including people without medical training. They argued this suggests Google’s AI may prioritise visibility and popularity over medical authority when summarising health information.
Google said the findings could not be generalised beyond Germany and stressed that many YouTube videos cited were produced by hospitals, clinics or licensed professionals. However, the study noted that such videos made up less than 1% of all YouTube links used in health-related AI Overviews.
Experts said the results indicate structural risks in how AI Overviews are designed, particularly for sensitive areas such as health, where misleading information could cause harm.
