Several clinical trials have been reported for ferric derisomaltose where it has been shown to be well tolerated and to improve markers of IDA. All clinical trials with ferric derisomaltose have been performed in adults, however, IDA is not specific to the adult population. In fact, children are likely to develop IDA due to their rapid growth. The aim in this trial is to evaluate the efficacy and safety of intravenous (IV) ferric derisomaltose in children 0 to \<18 years of age with IDA due to NDD-CKD or with IDA who are intolerant or unresponsive to oral iron . The subjects will receive ferric derisomaltose/iron isomaltoside 1000 (Monoferric®/Monofer®), at single doses of 10 mg/kg or 20 mg/kg with a maximal dose of 1000 mg. 24 subjects will be part of a PK assessment, meaning that more blood samples will be drawn within the first week after treatment. The blood samples will be used for analysis of the amount of total iron in the blood from treatment is given to day 7. For the individual subject, duration of the trial will be approximately 10 weeks (including a 14-day screening period) and each subject will attend 6-9 visits. Subjects who will be included in the PK assessments will attend 8 (subjects age 6 to \<12 years old and 0 to \<6 years old) or 9 (subjects age 12 to \<18 years old) visits, while the other subjects will attend 6 visits.

This is a combined clinical pharmacology and phase III study. The study is a prospective, open-label, multi-center study. Children 0 to \<18 years of age with iron deficiency anemia (IDA) with a) non-dialysis dependent chronic kidney disease (NDD-CKD) or b) who are intolerant or unresponsive to oral iron will be enrolled. The subjects will receive ferric derisomaltose/iron isomaltoside 1000 (Monoferric®) at single doses of 10 mg/kg or 20 mg/kg with a maximal dose of 1000 mg. A total of 200 subjects will be enrolled. Of these will 24 be part of the PK assessment. PK-subjects will be included in cohorts of 4 with the oldest age group as the first and with ferric derisomaltose 10 mg/kg to be increased to 20 mg/kg for the next cohort. Thus 12 subjects will be treated with 10mg/kg and the remaining 188 subjects with 20mg/kg.