User experiences and community responses to generative artificial intelligence health advice on reddit: topic modeling and content analysis study

Generative artificial intelligence (AI) chatbots are increasingly used for everyday health information seeking, yet little is known about how users interpret AI-generated health advice outside clinical encounters or how online communities respond when that advice is shared. This study examined how Reddit users describe their experiences with generative AI health advice and how communities respond to these accounts. We screened 8,715 unique posts from eight subreddits, posted between December 2022 and May 2026, and retained 2,521 relevant posts. Themes were identified using BERTopic. Posts were coded along four dimensions: purpose of AI use, emotional change attributed to AI, trust stance and verification orientation, and reported relationship to professional care. A further 43,899 comments were classified into nine response functions. All classification tasks were validated against human-coded samples (accuracy 0.79–0.94; macro-F1 0.68–0.91). Fourteen themes were identified among 2,521 retained posts. In 64.1%, authors described using chatbots to understand symptoms, test results, or possible diagnoses. In 26.3%, they said chatbot responses changed how they felt, including relief (12.6%) and alarm (11.5%). In 42.4%, authors expressed distrust or caution or continued checking chatbot advice against other sources; 8.9% described treating chatbots as their main source. Posts described advice, plans, or actions to seek, continue, or obtain more urgent professional care (24.0%), or to replace, delay, avoid, or reduce care (4.6%). Among comments assigned a substantive response function, sharing health information or personal experience was most common in the selected medical-advice subreddits and r/ClaudeAI. In the other three AI-product subreddits, replies most often presented chatbots as limited aids or warned about their limitations; in r/HealthAnxiety, they most often discouraged repeated reassurance seeking. Within this selected Reddit corpus, post authors mainly described using generative AI chatbots to understand health information, with accounts of both reassurance and heightened anxiety. Chatbot use was more often described in connection with seeking, continuing, or escalating professional care than with replacing, delaying, or reducing it. Post authors compared chatbot advice with other information sources, while peer responses interpreted, questioned, or contextualized that advice within a broader health-information ecosystem.