Google AI Overviews cite YouTube more than any medical site for health queries, study suggests | Google
Google’s search feature, AI Overviews, cites YouTube more than any medical website when answering questions about health issues, according to a study that raises new questions about a tool accessed by 2 billion people every month.
The company said its AI summaries, which appear at the top of search results and use generative AI to answer users’ questions, are “reliable” and cite reputable medical sources such as the Centers for Disease Control and Prevention and the Mayo Clinic.
However, a study analyzing responses to more than 50,000 health queries, captured using Google searches from Berlin, found that the most cited source was YouTube. The video sharing platform is the second most visited website in the world, after Google itself, and is owned by Google.
Researchers at SE Ranking, a search engine optimization platform, found that YouTube accounted for 4.43% of all AI Overview citations. No hospital network, government health portal, medical association or academic institution comes close to that figure, they said.
“This is important because YouTube is not a medical publisher,” the researchers wrote. “It is a general-purpose video platform. Anyone can upload content to it (e.g. board-certified doctors, hospital chains, but also wellness influencers, life coaches and creators without any medical training).”
Google told the Guardian that AI Overviews was designed to feature high-quality content from reputable sources, regardless of format, and that a variety of credible health authorities and licensed healthcare professionals have created content on YouTube. The results of the study cannot be extrapolated to other regions because they were conducted in Germany using German-language queries, the statement said.
The research comes after a Guardian investigation found people were at risk of harm due to false and misleading health information contained in Google AI preview responses.
In a case that experts called “dangerous” and “alarming,” Google provided false information about crucial liver function tests that could have left people with severe liver disease mistakenly thinking they were healthy. The company later removed AI previews for some, but not all, medical searches.
The SE Ranking study analyzed 50,807 healthcare-related prompts and keywords to see which sources AI Overviews relied on to generate answers.
They chose Germany because its healthcare system is strictly regulated by a mix of German and European guidelines, standards and safety regulations. “If AI systems rely heavily on non-medical or non-authoritative sources, even in such an environment, this suggests that the problem could extend beyond a single country,” they wrote.
AI insights appeared in more than 82% of health searches, the researchers said. When they looked at the sources that AI Overviews most often relied on for health-related answers, one result immediately stood out, they said. The most cited domain was YouTube with 20,621 citations out of a total of 465,823.
The second most cited source was NDR.de, with 14,158 citations (3.04%). The German public broadcaster produces health-related content as well as news, documentaries and entertainment. In third place is a medical reference site, Msdmanuals.com with 9,711 citations (2.08%).
The fourth most cited source was Germany’s largest consumer health portal, Netdoktor.de, with 7,519 citations (1.61%). The fifth most cited source was a career platform for doctors, Praktischarzt.de, with 7,145 citations (1.53%).
The researchers acknowledged the limitations of their study. It was taken as a point-in-time snapshot in December 2025, using German-language queries that reflected how German users typically search for health information.
Results may vary over time, by region and by question wording. However, even with these caveats, the results still cause concern.
Hannah van Kolfschooten, a researcher specializing in AI, health and law at the University of Basel who was not involved in the research, said: “This study provides empirical evidence that the risks posed by AI insights to health are structural and not anecdotal. It becomes difficult for Google to claim that misleading or health-harming results are rare cases.”
“Instead, the results show that these risks are built into the way AI insights are designed. In particular, the heavy reliance on YouTube rather than public health authorities or medical institutions suggests that visibility and popularity, rather than medical trustworthiness, are the central driver of health knowledge.”
A Google spokesperson said: “The implication that AI insights provide unreliable information is refuted by the report’s own data, which shows that the most cited domains in AI insights are reputable websites. And from what we saw in the published results, AI insights cited YouTube content from hospital and clinic experts.”
Google said the study showed that of the 25 most cited YouTube videos, 96% came from medical channels. However, researchers cautioned that these videos accounted for less than 1% of all YouTube health links cited by AI Overviews.
“Most of them (24 out of 25) come from medical sectors such as hospitals, clinics and health organizations,” the researchers write. “On top of that, 21 of the 25 videos clearly state that the content was created by an authorized or trusted source.
“So, at first glance, this seems rather reassuring. But it’s important to remember that these 25 videos represent only a tiny part (less than 1% of all YouTube links cited by AI Overviews). With the rest of the videos, the situation could be very different.”
