The LOS one-pager provides a concise overview of the Registry Study for Research of Blood Donor and Recipient Long-Term Outcome (LOS). This document is aimed at a wide audience, including patients, healthcare professionals, researchers and policy makers. It highlights the key aims and benefits of the LOS study, focusing on improving patient safety, adapting transfusion practices and increasing scientific knowledge through long-term data collection. The one-pager is useful for anyone who wants to understand the basic aspects of the LOS study and its implications for transfusion medicine. It serves as an introductory tool outlining the importance of the study, the stakeholders involved and the potential benefits for participants and the wider medical community.