The data: Two out of three YouTube videos about cancer or diabetes made by medical professionals don’t actually back up their claims with solid scientific evidence, according to a recently published study in JAMA Network Open. Researchers analyzed 309 YouTube health videos made in June 2025 by a range of physicians, pharmacists, and other clinicians. Videos averaged 19 minutes in length and 164,000 views (median).

Digging into the details: Researchers evaluated YouTube videos and rated the strength of evidence that supported healthcare professionals’ claims—most content failed to meet high clinical standards.

• Most videos received a “D” grade: About 63% of the videos earned this rating—the lowest possible grade—indicating their claims relied solely on anecdotes, personal experience, or unsupported assertions.
• Only 20% received an “A” grade: This grade indicates claims are backed up by studies that combine data from multiple independent studies or that follow official clinical guidelines from credible health organizations.
• The rest (18%) fell into intermediate rankings: About 15% received a “B” grade, and 3% received a “C” for making claims supported by specific clinical trials or high-quality observational studies, but with less rigor than the gold standard, or for making claims supported by smaller-scale observational studies.
• The study identified a negative correlation between scientific rigor and reach: Videos with the weakest evidence were 35% more likely to get higher view counts than videos grounded in strong scientific evidence.

Researchers did not conclude that medical professionals were intentionally spreading false information, but that their claims relied on weak empirical evidence and were therefore somewhat misleading.

Why it matters: YouTube has become the primary social media platform for health information.

• Among consumers who use social media for health information, 66% turn to YouTube, making it by far the most-used platform for health queries, per EMARKETER’s January 2026 Digital Health survey.
• That’s up from 52.9% in last year’s survey, when YouTube ranked second to Facebook among the top social platforms for health information.

YouTube’s support for longer-form video likely contributes to its growth as a health information destination, as it enables more nuanced and detailed discussions than most other social platforms.

Consumers act on health information they encounter on social media. In fact, 61% of those who seek health guidance there say they’ve followed advice from someone on social media—even when it contradicts their doctor’s recommendations, per our survey.

Implications for social media platforms: YouTube has tried to position itself as a credible hub for health content. It distinguishes authoritative content from misinformation, elevates professional sources through optional medical license verification, and partners with trusted institutions like the New England Journal of Medicine and the Cleveland Clinic to expand access to credible information on its platform.

The study proves that even with misinformation safeguards in place, a significant number of unverified medical claims will still slip through the cracks. Social media companies should team up with medical societies to develop clear, specific guidelines for clinician creators on what they should and shouldn’t claim about diseases and treatments in podcasts and videos.