Objectives: It is unclear how nurses adjust the double check during injectable medication administration andguarantee patient safety. We used the Functional Resonance Analysis Method (FRAM) to determine the fit betweenthe double check according to the protocol (work-as-imagined) and clinical practice (work-as-done). Weaimed to learn about process variation in order to optimize safety during injectable medication administration. Methods: A qualitative study (February-July 2018) with semi-structured group interviews. An internal medicineand a surgery ward of two Dutch hospitals participated (four wards total). We interviewed nurses about injectable medication administration practices, based on prior observations. A work-as-done model was constructedfor each hospital. The work-as-imagined model was based on the Dutch protocol for safe injectablemedication administration. Results: A total of 27 nurses were interviewed. In both hospitals, nurses split the double check into a digital andphysical check to improve workflow. The digital check was routinely conducted. For the physical check, nursesmade their own risk-impact analysis and assessed staffing, familiarity with the medication, severity of sideeffects, type of