Serum Hepcidin Immunoassay - Laboratory to Marketplace

This observational study is composed of two phases, and no investigational intervention agent. Oral iron therapy will be recommended by each subject's primary care clinician or his/her designate according to standard clinical care. There is no randomization. Subjects will be screened for enrollment by study personnel. Diagnostic Testing Phase (Study Visit 1). Enrolled subjects will have a study blood draw. Enrolled subjects will be assessed for presence of ID as defined by the reference standard: ID: Ferritin \< 20 ng/mL. Enrolled subjects will be assessed for presence of anemia as defined by: Anemia - Hemoglobin ≤ 11 g/dL Those determined to have ID and/or anemia and are prescribed oral iron therapy by their clinician will continue to the next phase in the study. For those without ID or anemia, or who meet Observation of Treatment Phase exclusion criteria, study participation will be complete. The expected duration of subject involvement for the Diagnostic Testing Phase is 1 week. Observation of Treatment Phase (Study Visits 2 and 3). Subjects identified as having ID and/or anemia and who have been prescribed oral iron therapy by their physician according to standard of care, and do not meet Observation of Treatment Phase exclusion criteria, will continue to the Observation of Treatment Phase of the study. The optimal dose, frequency, and timing of oral iron therapy are unknown and are based more on clinical experience than evidence. In 1998, based on expert opinion, the Centers for Disease Control (CDC) suggested 3 mg/kg/day of elemental iron for treatment of IDA in children. Patients with ID who do not have anemia (LID) should also have their iron stores repleted with treatment dose iron supplement. Given the effects of acute/chronic disease on serum ferritin and the dietary/diurnal variation of serum iron/TfSat, the absence of biochemical evidence of ID on a single measure does not rule out ID that may respond to empiric supplementation. Therefore, patients with anemia but without biochemical evidence of ID (AneID) may have masked ID and treatment with a finite course of supplemental iron therapy is unlikely to result in harm and may improve hemoglobin. Thus, we expect all subjects with ID and/or anemia will be recommended treatment by their clinician with ferrous sulfate at treatment at standard doses for adolescents and young adults of 3-5 mg elemental iron/kg/day, up to a maximum of 195 mg of elemental iron per day. Investigators will provide responsible clinicians with recommendations for ferrous sulfate treatment along with references to relevant clinical guidelines and research. The clinicians will be asked to provide the research team confirmation that the patient followed the oral iron treatment recommendations. If they did not, they will be asked to indicate what treatment, if any, they did advise for the subject. Subjects who continue to the Observation of Treatment Phase will have two follow-up visits and laboratory testing, including a study draw for hepcidin at each visit, to assess response to oral iron supplementation at: * 4-5 weeks (+/- 7 days) of therapy, and * 12 weeks (+/- 7 days) of therapy.