Iron deficiency (ID) is a common and challenging problem in adolescence. In order to prevent, recognize, and treat ID in this age range, it is critical to understand the recommended daily intake of iron in relation to an adolescent's activity, dietary habits, and basal iron losses. Adolescents following vegetarian or vegan diets exclusively rely on plant-based, nonheme iron, which has decreased bioavailability compared with heme iron and requires increased total iron intake. Individuals with disordered eating habits, excessive menstrual blood loss, and certain chronic health conditions (including inflammatory bowel disease and heart failure) are at high risk of ID and the development of symptomatic iron deficiency anemia (IDA). Adolescent athletes and those with sleep and movement disorders may also be more sensitive to changes in iron status. Iron deficiency is typically treated with oral iron supplementation. To maximize iron absorption, oral iron should be administered no more than once daily, ideally in the morning, while avoiding foods and drinks that inhibit iron absorption. Oral iron therapy should be provided for ≥3 mo in the setting of ID to reach a ferritin of 20 ng/mL before discontinuation. Intravenous iron is being increasingly used in this population and has demonstrated efficacy and safety in adolescents. It should be considered in those with persistent ID despite a course of oral iron, severe and/or symptomatic IDA, and chronic inflammatory conditions characterized by decreased gastrointestinal iron absorption.