Google’s AI Overviews feature most frequently cites YouTube when answering health-related search queries, according to a new study that raises concerns about how medical information is sourced for a tool used by around 2 billion people each month.
Researchers at SE Ranking analysed more than 50,000 German-language health queries and found that YouTube accounted for 4.43% of all citations used in AI Overviews, making it the single most cited source. No hospital network, government health body or academic institution came close. The next most cited sites were German public broadcaster NDR.de (3.04%) and the medical reference site Msdmanuals.com (2.08%).
The researchers warned that YouTube “is not a medical publisher” and allows content from anyone, including non-medical influencers, even though some videos are produced by qualified professionals. They said the findings suggest AI Overviews may prioritise popularity and visibility over medical authority.
Google responded that AI Overviews are designed to surface high-quality information regardless of format and said many YouTube videos cited come from hospitals and licensed professionals. It added that the study was limited to Germany and could not be generalised globally.
Independent experts said the results point to structural risks in how AI Overviews handle health information. Hannah van Kolfschooten, an AI and health researcher at the University of Basel, said the heavy reliance on YouTube suggests “medical reliability is not the central driver” of what users see.
The study follows earlier reporting that found misleading and potentially dangerous health information appearing in Google AI Overviews, prompting renewed scrutiny of how the system handles medical queries.
