This guideline provides a global, evidence-informed recommendation on daily iron supplementation in menstruating adult women and adolescents, as a public-health intervention for the prevention of anaemia and iron deficiency. The guideline aims to help Member States and their partners in their efforts to make informed decisions on the appropriate nutrition actions to achieve the Sustainable Development Goals, in particular, Goal 2: End hunger, achieve food security and improved nutrition and promote sustainable agriculture. It will also support Member States in their efforts to achieve the global targets set in the Comprehensive implementation plan on maternal, infant and young child nutrition, as endorsed by the Sixty-fifth World Health Assembly in 2012, in resolution WHA65.6, and the Global strategy for women’s, children’s and adolescents' health (2016–2030). The recommendation in this guideline is intended for a wide audience, including policy-makers, their expert advisers, and technical and programme staff at government institutions and organizations involved in the design, implementation and scaling-up of programmes for anaemia prevention and control, and in nutrition actions for public health. This guideline is intended to contribute to discussions among stakeholders when selecting or prioritizing interventions to be undertaken in their specific context. This document presents the key recommendation and a summary of the supporting evidence.