Secure and scalable electronic medical record (EMR) sharing is essential for cross-institutional collaboration, yet existing blockchain-based approaches can incur high on-chain overhead under bursty, fine-grained, and temporary authorization. We propose Secure and Scalable Tokenized EMR Sharing on a Permissioned Blockchain, referred to as SST-MedChain, a patient-centric framework that (i) enables patient-side non-interactive delegation via an Elliptic Curve Diffie–Hellman (ECDH)-derived verification token protected by a hash commitment, and (ii) reduces on-chain authorization to a near constant-time token lookup and atomic state transition using one-time access tokens. SST-MedChain further supports policy-bounded cascading re-delegation and fast revocation over deployment-bounded delegation chains via a Nested Freezing state machine and a Source Circuit Breaker. Experiments on FISCO BCOS (a permissioned blockchain platform) in a wide area network (WAN) show that, on the evaluated on-chain confirmation path, SST-MedChain improves throughput by 38% and reduces latency by 86% compared with Attribute-Based Access Control (ABAC) at 300 queries per second (QPS), and achieves 16.5% higher throughput than MedShare at 1000 QPS with comparatively stable average confirmation latency.