Iron deficiency is the leading cause of anemia among populations in industrialized and developing countries throughout the world. Here we will also highlight the heterogeneous etiology of IDA and we will discuss about the mechanisms involved in the clinical presentation, that is to say about diagnostic clues different taking into considerations some specific populations like women, children and elderly. The review also covers new insights into the genetics of IDA, such as iron refractory iron deficiency anemia (IRIDA) and also highlights prevalence of IDA in chronic disease and surgery. The impact of IDA on behaviour and cognition, physical function, quality of life, and pregnancy outcome are highlighted. An awareness of these patterns is important for pre-emption, early diagnosis and appropriate treatment.