A Trial Comparing the Incidence of Hypophosphatemia in Relation to Treatment With Iron Isomaltoside and Ferric Carboxymaltose in Subjects With Iron Deficiency Anaemia Due to Inflammatory Bowel Disease

Inclusion Criteria include: * Men or women ≥ 18 years * Subjects diagnosed with IBD * Hb \< 13 g/dL * Body weight ≥ 50 kg * S-ferritin \<100 ng/mL * eGFR ≥ 65 mL/min/1.73 m2 * S-phosphate \> 2.5 mg/dL * Oral iron preparations are ineffective or cannot be used or where there is a clinical need to de-liver iron rapidly * Willingness to participate and signing the Informed Consent Form (ICF) Exclusion Criteria include: * Anaemia predominantly caused by factors other than IDA according to Investigator's judgment * Hb ≥ 10 g/dL and body weight \< 70 kg * Hemochromatosis or other iron storage disorders * Known hypersensitivity reaction to any component of iron isomaltoside or ferric carboxymaltose * Previous serious hypersensitivity reactions to any IV iron compounds * Treatment with IV iron within the last 30 days prior to screening * Treatment with erythropoietin or erythropoietin-stimulation agents, red blood cell transfusion, radiotherapy, and/or chemotherapy within the last 30 days prior to screening * Received an investigational drug within the last 30 days prior to screening * Planned surgical procedure within the trial period * hepatic enzymes \> 3 times upper limit of normal * Surgery under general anaesthesia within the last 30 days prior to screening * Any non-viral infection within the last 30 days prior to screening * Alcohol or drug abuse within the past 6 months * Untreated hyperparathyroidism * Kidney transplantation * Conditions that interfere with the subject's ability to understand the requirements of the trial and/or presumable non-compliance * 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 * Pregnant or nursing women.