Open-label PK Study of Iron Isomaltoside 1000 (Monofer) Administered by 500 mg IV Injection or 1000 mg IV Infusion to Patients With Inflammatory Bowel Disease

Inclusion Criteria: 1. Men and women, aged more than 18 years 2. Subjects diagnosed with inflammatory bowel disease and mild to moderate disease activity (defined as a score of less than or equal to 5 on the Harvey-Bradshaw index for Crohn's disease and a Mayo score (subscore without endoscopy) of less than or equal to 6 for ulcerative colitis) 3. Weight above 50 kg 4. Hb \<12 g/dL (7.45 mmol/L) 5. Transferrin saturation (TfS) \<20% 6. Life expectancy beyond 12 months by investigator's judgment 7. Willingness to participate after informed consent - Exclusion Criteria: 1. Anaemia predominantly caused by other factors than iron deficiency anaemia 2. Iron overload or disturbances in utilisation of iron (e.g. haemochromatosis and haemosiderosis) 3. Drug hypersensitivity (i.e. previous hypersensitivity to Iron Dextran or iron mono- or disaccharide complexes or to iron sulphate) 4. Known hypersensitivity to any excipients in the investigational drug products 5. Subjects with a history of multiple allergies 6. Active Intestinal Tuberculosis 7. Active intestinal amoebic infections 8. Decompensated liver cirrhosis and hepatitis (Alanine Aminotransferase (ALT) \> 3 times upper limit normal) 9. History of immunocompromise and/or history of Hepatitis B and/or C 10. Acute infections (assessed by clinical judgment), supported by white blood cells (WBC) and C-reactive protein (CRP)) 11. Rheumatoid arthritis with symptoms or signs of active joint inflammation 12. Pregnancy and nursing (To avoid pregnancy, women have to be postmenopausal (at least 12 months must have elapsed since last menstruation), surgically sterile, or women of child bearing potential must 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: Contraceptive pills, intrauterine devices (IUD), contraceptive depot injections (prolonged-release gestagen), subdermal implantation, vaginal ring, and transdermal patches) 13. Extensive active bleeding necessitating blood transfusion 14. Planned elective surgery during the study 15. Participation in any other clinical study within 3 months prior to screening 16. Untreated B12 or folate deficiency 17. Other I.V. or oral iron treatment or blood transfusion within 4 weeks prior to screening visit 18. Erythropoietin treatment within 4 weeks prior to screening visit 19. Any other medical condition that, in the opinion of Investigator, may cause the patient to be unsuitable for the completion of the study or place the patient at potential risk from being in the study. Example: Uncontrolled Hypertension, Unstable Ischemic Heart Disease or Uncontrolled Diabetes Mellitus