Inclusion Criteria:  Subjects <18 years Informed consent and child assent, as age-appropriate, obtained before any trial- related activities and willingness to participate. LAR of the subject must sign and date the ICF (according to local requirements). The child must sign and date the CAF or provide oral assent, if required according to local requirements IDA caused by different etiologies such as gastrointestinal disease, NDD-CKD, or other conditions leading to IDA Hb concentration less than the 5th percentile for age and sex-specific reference range (Appendix B)  Subjects with NDD-CKD (a) or who are intolerant or unresponsive to oral iron (b):  a) Subjects with NDD-CKD:  TSAT ≤35 % or s-ferritin <100 ng/mL Estimated glomerular filtration rate (eGFR) <60 mL/min/1.73m2  If on ESA, receiving stable ESA regimen defined as dose adjustments no more than  ± 20 % for ≥8 weeks prior to screening  b) Subjects with documented history of intolerance or unresponsiveness to oral iron therapy for at least one month prior to trial enrolment.  TSAT ≤20 % or s-ferritin <100 ng/mL  Exclusion Criteria:  Anemia caused by factors other than IDA according to Investigator's judgment S-ferritin >600 ng/mL Hb ≤5.0 g/dL Iron overload or disturbances in utilization of iron (e.g. hemochromatosis and hemosiderosis) ALAT and/or ASAT >2 times upper limit of normal (e.g. decompensated liver cirrhosis or active hepatitis) Pregnant or nursing female subjects. In order to avoid pregnancy, female subjects of childbearing potential have to use adequate contraception (e.g. intrauterine devices, hormonal contraceptives, or double barrier method) or be abstinent during the whole trial period and 7 days after the last dosing. Childbearing potential refers to all female subjects ≥12 years old or <12 years old who have started menstruating Previous serious hypersensitivity reactions to any IV iron compounds including ferric derisomaltose Received an investigational drug within 30 days prior to screening Treatment with IV iron within 10 days prior to screening Treatment with blood transfusion, radiotherapy, chemotherapy or other drugs that suppress the bone marrow, and drugs which have anemia as side effect within 30 days prior to screening Planned elective surgery (or planned surgery during the trial period) where significant blood loss is expected within the last 30 days prior to screening Any non-viral infection (non-viral infection that has been fully treated before the baseline visit is accepted) Any other laboratory abnormality, medical condition, or psychiatric disorders which, in the opinion of the Investigator, will put the subject's disease management at risk or may result in the subject being unable to comply with the trial requirements