Iron deficiency (ID) affects billions of people worldwide and remains the leading cause of anemia with significant negative impacts on health. Our approach to ID and iron deficiency anemia (IDA) involves three steps (I3): (1) identification of ID/IDA, (2) investigation of and management of the underlying etiology of ID, and (3) iron repletion. Iron repletion options include oral and intravenous (IV) iron formulations. Oral iron remains a therapeutic option for the treatment of ID in stable patients, but there are many populations for whom IV iron is more effective. Therefore, IV iron should be considered when there are no contraindications, when poor response to oral iron is anticipated, when rapid hematologic responses are desired, and/or when there is availability of and accessibility to the product. Judicious use of red cell blood transfusion is recommended and should be considered only for severe, symptomatic IDA with hemodynamic instability. Identification and management of ID and IDA is a central pillar in patient blood management.