This WHO guideline provides evidence-based recommendations on daily iron supplementation in menstruating adult women and adolescents, as a public health intervention for the prevention of anemia and iron deficiency. The recommendation in this guideline is intended for a wide audience, including policymakers, their expert advisers, and technical and program staff at government institutions and organizations involved in the design, implementation, and scale-up of programs for anemia prevention and control, and in nutrition actions for public health. It includes recommendations for iron supplementation in countries where malaria is prevalent.