Medication-related harm is considered preventable if it occurs as a result of an identifiable, modifiable cause and its recurrence can be avoided by appropriate adaptation to a process or adherence to guidelines. Understanding the prevalence, nature and severity of preventable medication-related harm is critical for setting targets for clinically relevant, implementable improvements in patient safety. This report presents an updated systematic review and meta-analysis of studies of the prevalence, nature and severity of preventable medication-related harm in the international literature including in low- and middle-income countries (LMICs). The main target audience is policy makers, health care leaders, researchers and academics, practicing clinicians and advocacy groups on medication safety.