Google's AI Health Tool Relies Heavily on YouTube Over Medical Authorities
Google's AI Overviews feature, which provides generative AI summaries at the top of search results, cites YouTube more frequently than any medical website when responding to health-related queries, according to new research. This finding raises significant questions about the reliability of a tool viewed by approximately 2 billion people every month.
Study Reveals Startling Citation Patterns
A comprehensive study conducted by SE Ranking, a search engine optimisation platform, analysed responses to over 50,000 health queries captured through Google searches in Berlin. The research discovered that YouTube constituted 4.43% of all AI Overview citations for health information. No hospital network, government health portal, medical association, or academic institution came close to matching this level of citation frequency.
The researchers emphasised the importance of this finding by stating: "This matters because YouTube is not a medical publisher. It is a general-purpose video platform. Anyone can upload content there, including board-certified physicians and hospital channels, but also wellness influencers, life coaches, and creators with no medical training whatsoever."
Detailed Breakdown of Citation Sources
The study examined 50,807 healthcare-related prompts and keywords to identify which sources AI Overviews relied upon when generating answers. Researchers selected Germany for their investigation due to its strictly regulated healthcare system governed by German and EU directives, standards, and safety regulations.
AI Overviews appeared on more than 82% of health searches analysed. When examining citation patterns, researchers found:
- YouTube received 20,621 citations out of 465,823 total citations, making it the most cited domain
- NDR.de, a German public broadcaster producing health content, followed with 14,158 citations (3.04%)
- Msdmanuals.com, a medical reference site, ranked third with 9,711 citations (2.08%)
- Netdoktor.de, Germany's largest consumer health portal, came fourth with 7,519 citations (1.61%)
- Praktischarzt.de, a career platform for doctors, placed fifth with 7,145 citations (1.53%)
Google's Response and Research Limitations
Google responded to the findings by stating that AI Overviews was designed to surface high-quality content from reputable sources regardless of format. The company noted that a variety of credible health authorities and licensed medical professionals create content on YouTube. Google also pointed out that the study's findings could not be extrapolated to other regions since it was conducted using German-language queries in Germany.
The researchers acknowledged several limitations to their study:
- The research was conducted as a one-time snapshot in December 2025
- It used German-language queries reflecting how users in Germany typically search for health information
- Results could vary over time, by region, and depending on question phrasing
Expert Concerns About Structural Risks
Hannah van Kolfschooten, a researcher specialising in AI, health, and law at the University of Basel who was not involved with the study, commented: "This study provides empirical evidence that the risks posed by AI Overviews for health are structural, not anecdotal. It becomes difficult for Google to argue that misleading or harmful health outputs are rare cases."
She continued: "Instead, the findings show that these risks are embedded in the way AI Overviews are designed. In particular, the heavy reliance on YouTube rather than on public health authorities or medical institutions suggests that visibility and popularity, rather than medical reliability, is the central driver for health knowledge."
Contrasting Perspectives on Video Content Quality
Google highlighted that the study showed 96% of the 25 most cited YouTube videos came from medical channels. However, researchers cautioned that these videos represented fewer than 1% of all YouTube links cited by AI Overviews on health topics.
The researchers noted: "Most of them (24 out of 25) come from medical-related channels like hospitals, clinics and health organisations. On top of that, 21 of the 25 videos clearly note that the content was created by a licensed or trusted source. So at first glance it looks pretty reassuring. But it's important to remember that these 25 videos are just a tiny slice of all YouTube links AI Overviews actually cite."
This research follows previous Guardian investigations that found people were being put at risk by false and misleading health information in Google AI Overviews responses. In one particularly concerning case, Google provided inaccurate information about crucial liver function tests that could have led people with serious liver disease to incorrectly believe they were healthy.
