The revolution in the Internet of Things (IoT) is redesigning and reshaping the healthcare system technologically, economically and socially. The emerging and rapidly growing IoT-based Smart Healthcare System (SHCS) is seen as a sustainable solution to reduce the burden on the existing healthcare system due to increasing diseases and limited medical infrastructure. IoT-based SHCS plays a vital role in delivery of healthcare services in rural and remote areas where the essential medical amenities, necessary infrastructures and qualified medical practitioners are not available. Therefore, in this paper, a comprehensive investigation of futuristic IoT-based SHCS and its constituents is presented. This paper provides exhaustive review on different techniques and technologies dealing with smart healthcare framework, physiological sensing, signal processing, data communication, cloud computing and data analytics used in IoT-based SHCS. A comparative analysis of existing literature has been carried out to identify the recent trends and advancements in this very dynamic field of global importance. In addition to this, it highlights different issues and challenges, along with the recommendation for further research in the field. The prime objective of this paper is to deliver the state-of-the-art understanding and update about IoT-based SHCS and its constituents by providing a good source of information to the researchers, service providers, technologists, medical practitioners and the general population.