Health information portals (HIP) are gateways to reliable and personalised online health information. In practice, however, searching for information in HIP is still far from being effective due to the intricate nature of health information provision. Previous studies have shown the emerging trend of using domain ontology to address the retrieval issue in online healthcare information. Yet, the suitability of domain ontology alone for HIPs is still questionable due to the varied levels of user behaviour and preferences in information search. Inspired by this problem, we propose an ontology development method grounded on the collaboration between user warrant principles, knowledge engineering, and design science framework. The paper reports the development method and the implementation of such an user-warrant ontology that accommodates user-sensitivity into HIP. The evaluation process is conducted by domain experts responsible for portal management and validates the external semantic of the ontology according to a set of pre-defined evaluation criteria. Results from the application of this methodology to an actual HIP are also reported as this research demonstrates the potential of user warrant ontology to resolve information retrieval problem in HIP.