Four Key Biases in Influencers’ Medical Advice: The Risks and How to Reduce Them

Medical advice from social media influencers reaches millions of people every day—often far more than traditional news media—yet they are still perceived as private individuals and therefore evade any form of editorial responsibility. While influencers have become an important information source, their guidance is often incomplete, biased, or misleading. In our new analysis, published in The BMJ, we outline the key biases in influencers’ messaging and how to respond in order to mitigate the associated risks.

Four key biases that shape influencer health advice

Our analysis identifies four recurring sources of bias in influencer content:

• Lack of medical expertise: Many influencers do not have formal training in medicine or health sciences, yet they recommend diagnostic tests, treatments, or supplements as if they were experts. This increases the risk of promoting ineffective or harmful interventions.

• Industry influence: Influencers often collaborate with brands that provide payments, free products, or affiliate commissions. These commercial incentives can shape the content they share, especially when advertising is not properly disclosed.

• Entrepreneurial interests: Some influencers market their own health products, including supplements or tests. The desire to boost sales can lead to exaggerated claims or the promotion of unproven interventions.

• Personal beliefs: Health recommendations may also reflect personal ideologies—such as alternative medicine, anti-vaccine views, or lifestyle philosophies—that are not supported by scientific evidence.

These biases are amplified by parasocial relationships: one-sided emotional connections that make followers feel they “know” the influencer. This sense of familiarity increases trust and makes persuasive health messaging more effective.

Examples illustrate how this plays out in practice.

A widely discussed case is Kim Kardashian’s promotion of full-body MRI screening—a test without proven health benefit and with considerable risks of overdiagnosis. Another example is “Dr. Eric Berg,” a US chiropractor with a large online following who promotes high-dose supplements and sells his own branded products, some of which have received regulatory warnings due to concerning ingredient levels (for more examples see Table 1, from BMJ analysis).

Representative survey results show strong influence on young people

The risks highlighted in the BMJ analysis are supported by findings from our recent study published in the Journal of Adolescent Health. This study examined how 15- to 25-year-olds in Austria interact with influencers and how this shapes their health decisions.

Key findings include:

• Young people estimate that over 50% of the content in their feeds comes from influencers.

• More than 80% encounter influencer health content at least occasionally.

• 53% have already purchased a product because of influencer recommendations. – including supplements (31%), addictive substances (15%), medications (13%), and medical self-tests (11%).

• 78% say they trust the influencers they follow “at least somewhat”—a similar level of trust as in traditional media.

• Problematic social media use and strong parasocial relationships are associated with higher susceptibility to influencer marketing.

• Digital health literacy has a protective effect: young people with higher perceived competence are less likely to buy health-related products based on influencer endorsement.

These findings indicate that influencers hold substantial persuasive power—power that is often underestimated in public health discussions.

A need for coordinated action

While some influencers contribute positively by explaining medical topics or correcting misinformation, the overall digital environment remains difficult to navigate. Our BMJ analysis highlights the need for coordinated action among governments, digital platforms, health institutions, and educators.

• The EU’s Digital Services Act requires major platforms to assess and mitigate systemic health risks, such as the spread of misleading medical content.

• National governments can assign more editorial responsibility to high-reach influencers and restrict harmful health advertising.

• Strengthening digital and health literacy, particularly among young people, is essential for helping users recognise commercial, ideological, or manipulative content.

Together, these strategies can create a safer digital information environment in which reliable medical advice is easier to identify and harmful content is less likely to spread.

The BMJ

Heiss, R., Woloshin, S., Dave, S., Engel, E., Gell, S., & Willis, E. (2025). Responding to public health challenges of medical advice from social media influencers. The BMJ. https://www.bmj.com/content/391/bmj-2025-086061

Click here for free full-text PDF.

Journal of Adolescent Health

Engel, E., Gell, S., Karsay, K., Heiss, R. (2025). Engagement with Influencers as Sources of Health Information and Product Promotions: A Cross-Sectional Survey of Austrian Youth Aged 15–25. Journal of Adolescent Health. https://www.jahonline.org/article/S1054-139X(25)00415-X/fulltext 

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