Iron deficiency is the most common nutrient deficiency in the world, the leading cause of anemia in about 2 billion people. It mainly affects children, pre-menopausal women, and residents of low-income and middle-income countries. Iron deficiency anemia (IDA) is one of the many consequences of iron deficiency, but clinical and functional disorders can occur without anemia. Iron deficiency in erythroblasts and other tissues occurs when total iron stores in the body are low or when inflammation causes iron retention in the plasma, primarily due to the effects of hepcidin, a significant regulator of systemic iron homeostasis. Since the issue of iron deficiency and iron deficiency disease is a global problem, the fight against anemia is now a global health priority. In this context, this review addresses iron metabolism, diagnosis, and clinical management of patients with iron deficiency and IDA and considers the prospects for the use of low-dose oral iron supplements for the prevention and treatment of iron deficiency.