A Generative AI Architecture Integrating Retrieval-Augmented Generation and Low-Rank Adaptation for Knowledge-Intensive Medical Reasoning

Large language models (LLMs) have demonstrated strong potential in medical knowledge applications; however, their reliability in knowledge-intensive medical reasoning—remains limited due to hallucination, inadequate domain grounding, and unstable inference behavior. These limitations are particularly pronounced in tasks of professional medical reasoning that require strict logical consistency and authoritative knowledge support. This study proposes a generative AI architecture that integrates RAG (Retrieval-Augmented Generation) with parameter-efficient supervised fine-tuning based on Low-Rank Adaptation (LoRA) to improve reasoning stability and diagnostic accuracy in complex medical domains. The architecture combines internalized domain reasoning learned through LoRA-based fine-tuning with external knowledge grounding enabled by a dynamic RAG mechanism, allowing the model to selectively retrieve domain-specific knowledge only when it is semantically relevant and evidence supported. To validate the proposed architecture, a large-scale real-world dataset comprising 11,476 multiple-choice questions from Taiwan’s national Traditional Chinese Medicine (TCM) licensing examinations (2005–2025) is constructed as a representative case study of knowledge-intensive medical reasoning. The experimental results show that the baseline LLM achieves an accuracy of 61.0%. Incorporating RAG improves accuracy to 89.0%, while combined LoRA-based fine-tuning and RAG architecture further increases accuracy to 90.1%, with reduced variance across repeated evaluations. Statistical analysis using McNemar’s test confirms that the performance improvements introduced by the retrieval mechanism are highly significant. The results demonstrate that integrating parameter-efficient fine-tuning with dynamically controlled retrieval is critical to balancing reasoning stability and knowledge enhancement in generative AI systems. Beyond the specific medical case study examined in this work, the proposed architecture offers a reproducible and extensible framework for developing reliable generative AI systems in other knowledge-intensive professional reasoning and educational domains.