Accurate medical diagnosis often relies on both textual self-reported symptoms and structured medical examination results of patients. However, these examinations vary significantly in cost—measured in time, money, or patient discomfort---creating a challenging trade-off between diagnostic accuracy and resource efficiency. To address this issue, we propose a dynamic diagnostic framework that incrementally selects medical examinations based on individual characteristics of each patient. Starting with textual self-reported symptoms and basic demographic, the system determines follow-up examinations step-by-step, improving accuracy while minimizing additional costs. Specifically, we introduce Dynamic feature selection with Instance-Specific Cost sensitivity (DISC). DISC treats each examination as a feature and learns to acquire them sequentially to optimize predictive performance under personalized cost constraints. To support richer clinical understanding, we further develop a multimodal framework that integrates unstructured self-reported symptom text with structured medical examination data. We conduct experiments on 680,000 patients with 43 million medical examination records, demonstrating that DISC high diagnostic accuracy even when accounting for examination costs. Our work provides substantial momentum for the advancement of AI in healthcare, offering both methodological and practical foundations that can significantly accelerate the deployment of intelligent, cost-aware diagnostic systems in real-world clinical settings.