Optimizing Dosing Strategies in Oral Iron Supplementation

Inclusion Criteria: * Informed Consent signed by the subject * ≥18 years of age * Iron deficiency: Ferritin \<30 µg/l * hemoglobin ≥ 80 g/l * CRP \< 5 mg/l Exclusion Criteria: * Refusal of study participation, * Regular administration of Erythropoietin * Oral or intravenous iron supplementation \<12 weeks prior to investigation * Contraindications to intervention medication (Tardyferon), e.g. known hypersensitivity or allergy to iron sulfate / ferrous sulfate * Blood transfusion or donation \<12 weeks prior to investigation * Active chemotherapy * Inability to follow the procedures of the investigation, e.g. due to language problems, psychological disorders, dementia, etc. of the subject. Note Due to slow recruitment, the following inclusion criterion was removed on 09/25/2024 (MM/DD/YYYY): Anemia (as defined by the WHO): Hemoglobin \<130 g/L for men, Hemoglobin \<120 g/l for women, Hemoglobin \<110 g/l for pregnant women