Drug shortages occur when the demand of a drug exceeds the supply and are an ongoing issue in the U.S. healthcare system, although the number and severity of shortages has changed over time. While the overall number of shortages may be lower than it was more than a decade ago, the causes and impacts have shifted, requiring different strategies to resolve and prevent shortages. All stakeholders involved in the supply and distribution of medicines, from active ingredient manufacturers to pharmacists, play a role in preventing shortages and ensuring patient access to medicines.As of June 2023, there are 132 molecules in the U.S. market with active shortages, impacting a range of therapy areas including pain/anesthesia, oncology, central nervous system, and infectious disease. Over the past five-and-a-half years, three times as many new molecule shortages have occurred as have been resolved, with shortages typically lasting more than a year.Shortages tend to be in generic (84%) and injectable drugs (67%) and are more frequently multi-source, while shortages were more often single-source generics in 2011, reflecting efforts by regulators and industry to increase generic approvals. Despite shortage molecules predominantly being multi-source, markets remain highly concentrated in a few suppliers, impacting the ability to readily resolve shortages when a leading supplier is affected, and new or existing manufacturers must build or expand manufacturing capacity to account for the gap in supply.