Shared decision making (SDM) is regarded as an ideal in chronic illness care but is difficult to implement in practice. Communication and reflection play an important role and need further investigation. Using grounded theory, we studied patient-provider interaction in a difficult and advanced area: managing poorly controlled diabetes. A person-centered communication and reflection model was developed, identifying SDM in chronic care to be a question of professionals gaining insight into patients' decisions, rather than the opposite. The model reveals important choices in communication and reflection, which were decisive for whether SDM was achieved or not. SDM involved co-creating person-centered knowledge: concrete evidence which empowered patients and professionals in problem solving. Although further testing is required, the general tenets of the model are expected to be applicable across chronic conditions. Findings indicate that SDM in chronic illness care requires innovation in current approaches to decision making and problem solving.