Background Increasing numbers of older people are living in the community with multiple diagnoses and medications. Managing multiple medications produces issues of unrivalled complexity for those involved. Despite a growing body of literature on the subject, gaps remain in understanding how, why and for whom complex medication management works, and therefore how best to improve practice and outcomes. MEMORABLE, MEdication Management in Older people: Realist Approaches Based on Literature and Evaluation, aimed to address these gaps. Methods MEMORABLE, a National Institute of Health Research funded project, used a realist approach to understand causal paths within medication management. Informed by RAMESES guidelines, MEMORABLE involved three overlapping work packages: 1) Realist Review of the literature (specifically 24 articles on medication management exploring causality); 2) Realist Evaluation (50 realist-informed interviews with older people, family carers and health and care practitioners, explaining their experiences); and 3) data synthesis and theorising from 1) and 2). Results The complexity of medication management was viewed from the perspective of ‘implementation’. This enabled the researchers to structure the medication management process into five iterative Stages; three individual Stages carried out by the older person on their own or with family carer support in which they are balancing routines, coping and risk; and two interpersonal Stages where the older person works with a practitioner-prescriber-reviewer, perhaps with carer involvement. Applying Normalisation Process Theory to this process, four steps were identified within each Stage: 1) sense making - information, clarification; 2) action - shared decision making; 3) reflection/monitoring; and 4) relationships that are enduring, based on collaboration and mutual trust. In a detailed analysis of Stage 5: Reviewing/reconciling medications, adopting the lens of ‘burden’, MEMORABLE identified five burdens amenable to mitigation: ambiguity, concealment, unfamiliarity, fragmentation and exclusion. Two initial improvement propositions were then set out for development through further research: a risk screening tool and individualised information.Conclusions By adopting a realist approach and synthesising rich data from evidence and experiential accounts, MEMORABLE has established a transferable evidence and experience-based, theoretical framework, focused on burden, to explore and explain the real world complexity of medication management for and with older people.