Aims: User involvement is pivotal for health development, but there are significant gaps in our understanding of the concept. The Copenhagen Diabetes Consensus on User Involvement in Diabetes Care, Prevention and Research (CODIAC) was established to address these gaps, share knowledge and develop best practices. Methods: A literature review of user involvement was undertaken in diabetes care, prevention and research. Moreover, a Group Concept Mapping (GCM) survey synthesized the knowledge and opinions of researchers, healthcare professionals and people with diabetes and their carers to identify gaps between what is important for user involvement and what is being done in practice. Finally, a consensus conference discussed the main gaps in knowledge and practice while developing plans to address the shortcomings. Results: The literature review demonstrated that user involvement is an effective strategy for diabetes care, prevention and research, given the right support and conditions, but gaps and key challenges regarding the value and impact of user involvement approaches were found. The GCM process identified 11 major gaps, where important issues were not being sufficiently practised. The conference considered these gaps and opportunities to develop new collaborative initiatives under eight overall themes. Conclusions: User involvement is effective and adds value to diabetes care, prevention and research when used under the right circumstances. CODIAC developed new learning about the way in which academic and research knowledge can be transferred to more practice-oriented knowledge and concrete collaborative initiatives. This approach may be a potential new framework for initiatives in which coherence of process can lead to coherent outputs.