Medication nonadherence is widely recognized as a common and costly problem.1 Approximately 30% to 50% of US adults are not adherent to long-term medications leading to an estimated $100 billion in preventable costs annually.1 The barriers to medication adherence are similar to other complex health behaviors, such as weight loss, which have multiple contributing factors. Despite the widespread prevalence and cost of medication nonadherence, it is undetected and undertreated in a significant proportion of adults across care settings. According to the World Health Organization, “increasing the effectiveness of adherence interventions may have far greater impact on the health of the population than any improvement in specific medical treatments.” How can adherence be improved? We propose that the first step is to view medication nonadherence as a diagnosable and treatable medical condition.