Objective To explore the impact of patient education on the lives of people with diabetes, including the effect on interactions with doctors and other healthcare professionals.

Design Qualitative user-led study using longitudinal interviews and 146 h of participant observation. Data were analysed using a narrative approach.

Participants 21 patients with type 1 diabetes, those either about to attend a patient education course or those who had completed the course in the previous 10 years.

Setting Established patient education centres in three UK teaching hospitals teaching the Dose Adjustment for Normal Eating (DAFNE) course.

Results Both postcourse and several years later, most participants spoke of the experience of taking part in education as life-changingly positive. It helped them understand how to gain control over a very complex disease and freed them from dependence on medical advice and restrictive regimes. However, interactions within the health system following patient education could be fraught. Participants emerged from the course with greater condition-specific knowledge than many of the healthcare professionals they encountered. When these professionals did not understand what their patients were trying to do and were uncomfortable trusting their expertise, there could be serious consequences for these patients' ability to continue effective self-management.

Conclusions Patients who have in-depth knowledge of their condition encounter problems when their expertise is seen as inappropriate in standard healthcare interactions, and expertise taught to patients in one branch of medicine can be considered non-compliant by those who are not specialists in that field. Although patient education can give people confidence in their own self-management skills, it cannot solve the power imbalance that remains when a generalist healthcare professional, however well meaning, blocks access to medication and supplies needed to manage chronic diseases successfully. There is a role for those involved in primary and hospital care, including those supporting and training healthcare professionals, to recognise these problems and find ways to acknowledge and respect chronic patients' biomedical and practical expertise.