Pilot Study: Randomized, Placebo-controlled Comparator Trial of IV vs Oral Iron Treatment of RLS With IDA. (IVOR-IDA)

Inclusion Criteria: * Diagnosis of RLS based on questionnaire and confirmed by Hopkins telephone Diagnostic Interview conducted by investigators or clinicians part of the study. * Iron deficiency anemia defined as ID either ferritin \<20 mcg/l, Tsat \<19%, anemia Hgb \<13 for both males and females. * Willingness to use contraceptive to avoid pregnancy: Women have to be surgically sterile, post-menopausal, or use one of the following contraceptives during the whole study period and after the study has ended for at least 5 times plasma biological half-life of the investigational medicinal product: intrauterine devices or hormonal contraceptives (contraceptive pills, implants, transdermal patches, hormonal vaginal devices, or injections with prolonged release). * Willingness to participate and signing the informed consent form. Exclusion Criteria: * Iron overload or disturbances in utilization of iron (e.g. haemochromatosis and haemosiderosis) * Decompensated liver cirrhosis or active hepatitis (ALAT \> 3 times upper limit of normal) * Serum ferritin \> 500 ng/mL or transferrin saturation \>40% * Active acute or chronic infections (assessed by clinical judgement that may be indicated by White Blood Cells (WBC) and C-Reactive Protein (CRP) when these are available) * Rheumatoid arthritis with symptoms or signs of active inflammation * Pregnant and nursing women * History of multiple allergies * Known hypersensitivity to parenteral or oral iron or any excipients in the drug products * Previous IV iron treatment for RLS * Other iron treatment or blood transfusion within 4 weeks prior to the screening or treatment visit * Planned elective surgery during the study * Current (past 4 weeks) use of drugs that treat RLS, e.g. opioids, alpha-2-delta anti-depressants, dopaminergics (dopamine promoters, dopamine antagonists/blockers) * Any other medical condition that, in the opinion of Investigator, may cause the subject to be unsuitable for the completion og the study or place the subject at potential risk from being in the study, e.g. a malignancy, uncontrolled hypertension, unstable ischemic heart disease, or uncontrolled diabetes mellitus.