Diabetes is a national health priority due to its increasing prevalence and the costly consequences of poor control, particularly for Maori. Better diabetes control results in fewer long-term complications such as blindness, amputations, and heart disease. Mobile phone-based interventions have potential to support people to self-manage their diabetes and improve their communications with their healthcare team. This study will look at the benefits of a text message-based programme developed by the National Institute for Health Innovation and Waitemata DHB for people with poorly controlled diabetes. Five hundred volunteers will be randomly assigned to receive either usual care alone or usual care plus the mHealth programme to use for 9 months. The main aims will be improved patient satisfaction with care and better diabetes control, which should reduce hospital visits and complications. This research will allow DHBs to make informed decisions on the use of technology-based support for self-management.