Multiple benefits (submitting healthcare bills to one or more organizations) and data breaches (tampering of healthcare data by healthcare organization authorities) are typical frauds happening due to the centralization of authority in healthcare systems. Preventing multiple benefits and data breaches can greatly lessen the huge losses to healthcare systems. In this paper, we propose an extended lightweight blockchain (ELB) based collaborative healthcare system for decentralizing the authority in healthcare organizations. The proposed architecture is rigorously tested in avoiding multiple benefits and data breaches and compared with the state-of-the-art methods. The experimental results evidenced that the proposed ELB architecture can effectively avoid multiple benefits and data breaches with less computation and communication overheads.