This study examines whether social media influencers can improve patient adherence to medical treatments. Based on a survey of 475 participants, it analyzes the roles of social attractiveness, perceived authenticity, and perceived expertise of Instagram influencers. Results show that influencers can positively affect adherence, mainly through authenticity and expertise. Emotional messages are more effective than rational ones in driving engagement and behavior change. Overall, influencers can support health communication, but credibility is crucial to avoid misinformation risks.