Iron deficiency (ID) without anaemia frequently remains undiagnosed when symptoms are attributed to ID with anaemia. Serum ferritin is the primary diagnostic parameter, whereas <10 microg/l represent depleted iron stores, 10-30 microg/l can confirm ID without anaemia and 30-50 microg/l might indicate functional ID. In case of increased CRP or ALT, normal/elevated ferritin should be interpreted with caution. Intravenous iron is indicated if oral iron is not effective or tolerated. At ferritin <10 microg/l, a cumulative dose of 1000 mg iron and at ferritin 10-30 microg/l, a cumulative dose of 500 mg is advised. At ferritin 30-50 microg/l a first dose of 200 mg might be considered. Ferritin shall be reassessed not sooner than 2 weeks after the last oral or 8-12 weeks after the last iv iron administration.