Medical QA systems powered by Retrieval-Augmented Generation (RAG) models support clinical decision-making but may introduce biases related to race, gender, and social determinants of health. We systematically evaluate biases in RAG-based LLM by examining demographic-sensitive queries and measuring retrieval discrepancies. Using datasets like MMLU and MedMCQA, we analyze retrieval overlap and correctness disparities. Our findings reveal substantial demographic disparities within RAG pipelines, emphasizing the critical need for retrieval methods that explicitly account for fairness to ensure equitable clinical decision-making.