We consent to many things in life, but sometimes we do not know what we consent to. When discussing data protection in Europe, consent has been associated with permission under the GDPR, and health data are highly sensitive. Patients cannot make an informed decision without being provided with the information they need upfront: no informed decision, no informed consent. This paper presents a consent management system for patient-generated health data stored with HL7 FHIR specification, tested on Type 1 diabetes synthetic data. This architecture, based on using FHIR as an unequivocal data exchange format, can lead to individuals (patients) taking control of their data, enabling potential data exchange and reuse of health data across countries and organisations, in line with the European Commission proposal of a European Health Data Space.