<p>The proliferation of Internet of Things (IoT) in healthcare has facilitated real-time data access, improved reliability, and transparency. However, existing healthcare IoT systems predominantly rely on centralized client-server architecture, making them susceptible to single points of failure and critical security vulnerabilities. As a result, transitioning to a decentralized paradigm is imperative to enhance security, resilience, and trust in healthcare systems. Blockchain technology, widely regarded as one of the most robust decentralized platforms, offers built-in security, transparency, immutability, resilience, and complete traceability, making it an optimal solution for securing healthcare IoT applications. However, achieving consensus in fault-tolerant distributed systems remains a significant challenge in blockchain networks. This paper presents a critical analysis of leading consensus algorithms, including Raft, Paxos, and EPaxos, assessing their applicability to blockchain-based healthcare solutions. To address existing security and authentication challenges, this paper proposes Secure-Authentication, a consortium blockchain-based mechanism that makes a distinct contribution by integrating a lightweight, multi-factor authentication protocol designed for real-time information sharing. Unlike existing schemes that treat authentication and consensus separately, our unified approach is specifically engineered for resource-constrained healthcare IoT environments. The proposed mechanism introduces import assurance and auto-validation features to mitigate risks like Loss of Value and Loss of Opportunity. Through rigorous simulation and formal verification using BAN logic and AVISPA, the proposed framework achieves provable security against common attacks while maintaining exceptional performance, with authentication latencies below 0.02 milliseconds. This work establishes a new paradigm for constructing efficient, secure, and resilient authentication systems for decentralized healthcare IoT.</p>