This review article by Wai Yin Lam and Paula Fresco provides an overview of medication adherence measures, emphasizing the importance of improving adherence to enhance health outcomes and reduce healthcare costs. The authors highlight that medication nonadherence is a significant public health issue, affecting up to 60% of patients with chronic diseases. They discuss the challenges in measuring adherence, including the lack of a gold standard method and the need for a balanced approach that considers reliability, practicality, and cost-effectiveness. The article categorizes medication adherence measures into subjective and objective categories. Subjective measures, such as self-reporting and clinician assessments, are useful for understanding patient beliefs and barriers but may suffer from underreporting. Objective measures, including pill counts, electronic monitoring, secondary database analysis, and biochemical markers, provide more precise records of medication-taking behavior but can be costly and intrusive. The authors detail various objective measures, such as the Medication Possession Ratio (MPR), Continuous Multiple Interval Measure of Medication Acquisition (CMA), and the Medication Events Monitoring System (MEMS), each with its strengths and limitations. They also discuss the use of electronic medication packaging (EMP) devices, pill counts, and clinician assessments and self-report questionnaires. The review emphasizes the importance of a multimeasure approach, combining multiple methods to capture the complexity of medication adherence. This approach can provide higher reliability and reveal more reasons for nonadherence. However, it also increases the complexity of analysis and interpretation. The article concludes by highlighting the need for further research to develop and validate new measures and improve existing ones, particularly for specific populations and conditions. It underscores the importance of healthcare professionals and researchers using all available methods to improve medication adherence and tailor interventions to individual patients.This review article by Wai Yin Lam and Paula Fresco provides an overview of medication adherence measures, emphasizing the importance of improving adherence to enhance health outcomes and reduce healthcare costs. The authors highlight that medication nonadherence is a significant public health issue, affecting up to 60% of patients with chronic diseases. They discuss the challenges in measuring adherence, including the lack of a gold standard method and the need for a balanced approach that considers reliability, practicality, and cost-effectiveness. The article categorizes medication adherence measures into subjective and objective categories. Subjective measures, such as self-reporting and clinician assessments, are useful for understanding patient beliefs and barriers but may suffer from underreporting. Objective measures, including pill counts, electronic monitoring, secondary database analysis, and biochemical markers, provide more precise records of medication-taking behavior but can be costly and intrusive. The authors detail various objective measures, such as the Medication Possession Ratio (MPR), Continuous Multiple Interval Measure of Medication Acquisition (CMA), and the Medication Events Monitoring System (MEMS), each with its strengths and limitations. They also discuss the use of electronic medication packaging (EMP) devices, pill counts, and clinician assessments and self-report questionnaires. The review emphasizes the importance of a multimeasure approach, combining multiple methods to capture the complexity of medication adherence. This approach can provide higher reliability and reveal more reasons for nonadherence. However, it also increases the complexity of analysis and interpretation. The article concludes by highlighting the need for further research to develop and validate new measures and improve existing ones, particularly for specific populations and conditions. It underscores the importance of healthcare professionals and researchers using all available methods to improve medication adherence and tailor interventions to individual patients.