Non-adherence to medical treatment or lack of perseverance over time is a worldwide health problem in all chronic conditions, especially asymptomatic ones. It has been estimated that only half of the patients comply with long-term therapy. A large proportion of patients discontinued treatment with BP, and a majority of these did not even renew their first prescription. Adherence, although enhanced by less frequent dosing, was suboptimal in all of its aspects, i.e. acceptance, persistence and compliance (Fig. 27.1). Furthermore, the risk of non-adherence increases with increased duration of treatment. In osteoporosis and osteopaenia, non-adherent patients have smaller decreases in rates of bone turnover, smaller increases in BMD and a greater risk of fracture. Patients may be encouraged to adhere when presented with results of measurements of BMD or bone turnover, indicating positive effects of the therapy. Compliance is also increased by utilisation of simplified and user-friendly treatment modalities such as tablets given weekly or monthly and infusions given every few months or annually. When discussing adherence or non-adherence, usually three definitions are used in the literature.