Digital twins (DTs) are emerging as a transformative paradigm in health care, combining continuous data from sensors, real-world insights from wearables, and predictive power from artificial intelligence (AI). These virtual patient replicas evolve in real time, enabling early disease detection, personalized simulation of treatment responses, and preventive interventions before symptoms appear. Recent advances in cardiology, oncology, and metabolic health illustrate how digital twins integrate multimodal data streams to generate actionable foresight. Coupled with blockchain for secure data exchange and patient consent, digital twins stand at the intersection of precision medicine and ethical innovation. This article explores the evolving role of digital twins in health care detection and preventive care, highlighting how sensors, wearables, and AI converge to reshape the future of clinical practice. This article also discusses privacy, interoperability, and regulatory guardrails.