MedRedFlag: Investigating how LLMs Redirect Misconceptions in Real-World Health Communication

Real-world health questions from patients often unintentionally embed false assumptions or premises. In such cases, safe medical communication typically involves redirection: addressing the implicit misconception and then responding to the underlying patient context, rather than the original question. While large language models (LLMs) are increasingly being used by lay users for medical advice, they have not yet been tested for this crucial competency. Therefore, in this work, we investigate how LLMs react to false premises embedded within real-world health questions. We develop a semi-automated pipeline to curate MedRedFlag, a dataset of 1100+ questions sourced from Reddit that require redirection. We then systematically compare responses from state-of-the-art LLMs to those from clinicians. Our analysis reveals that LLMs often fail to redirect problematic questions, even when the problematic premise is detected, and provide answers that could lead to suboptimal medical decision making. Our benchmark and results reveal a novel and substantial gap in how LLMs perform under the conditions of real-world health communication, highlighting critical safety concerns for patient-facing medical AI systems. Code and data are available at https://github.com/srsambara-1/ MedRedFlag . * Equal contribution. My Oura ring showed a resting heart rate of 20bpm last night -should I consider calling my doctor for a chest workup? Human physician redirects false assumption.... That resting heart rate doesn't sound like an accurate clinical measurement -you would be unresponsive! when LLMs accommodate patient misconceptions. Short answer: yes! That sounds dangerously low. You should consider heading to an ER. I just found a small bump under my armpit. I'm terrified. What are the best treatment options for lymphoma? Lymphoma is quite rare -based on your medical history, this seems like it could be a relatively benign skin irritation! You're not alone in this. A common list of treatment options for lymphoma includes chemotherapy and radiation.