The interoperability of healthcare data across various systems remains a big challenge, largely attributable to the disparate data schemas and APIs in use. This study showcases the integration of a FHIR layer into GameBus, a gamified health platform, aiming to enhance its interoperability. Traditionally, GameBus has relied on proprietary data schemas and REST APIs, which restricted data exchange with other platforms. The incorporation of the FHIR standard significantly mitigates these constraints. The FHIR layer, constructed with open-source technologies — including the Google HCLS Data Harmonization tool for data transformation and the HAPI FHIR framework for RESTful services — allows GameBus to engage in data sharing using standardized FHIR formats and APIs. Implemented as a standalone microservice, this layer requires no alterations to the pre-existing architecture of GameBus. Furthermore, the design and implementation of the FHIR layer illustrate a generic method for achieving interoperability across diverse healthcare platforms.