OBJECTIVE: To contextualise the degree of harm that comes from unsafe medical care compared with individual health conditions using the global burden of disease (GBD), a metric to determine how much suffering is caused by individual diseases. DESIGN: Analytic modelling of observational studies investigating unsafe medical care in countries' inpatient care settings, stratified by national income, to identify incidence of seven adverse events for GBD modelling. Observational studies were generated through a comprehensive search of over 16 000 articles written in English after 1976, of which over 4000 were appropriate for full text review. RESULTS: The incidence, clinical outcomes, demographics and costs for each of the seven adverse events were collected from each publication when available. We used disability-adjusted life years (DALYs) lost as a standardised metric to measure morbidity and mortality due to specific adverse events. We estimate that there are 421 million hospitalisations in the world annually, and approximately 42.7 million adverse events. These adverse events result in 23 million DALYs lost per year. Approximately two-thirds of all adverse events, and the DALYs lost from them, occurred in low-income and middle-income countries. CONCLUSIONS: This study provides early evidence that adverse events due to medical care represent a major source of morbidity and mortality globally. Though suffering related to the lack of access to care in many countries remains, these findings suggest the importance of critically evaluating the quality and safety of the care provided once a person accesses health services. While further refinements of the estimates are needed, these data should be a call to global health policymakers to make patient safety an international priority.