Aims: Iron deficiency anaemia (IDA) is common in patients with inflammatory bowel disease (IBD), who are often treated with intravenous iron. This observational study aimed to investigate the effectiveness and safety of iron isomaltoside in routine practical care of IDA in IBD patients.Methods: The study included 197 IBD patients designated for treatment with iron isomaltoside. Treatment was administered according to routine practice. Data were recorded at baseline and after approximately 4, 8, and 16 weeks. Efficacy data included haemoglobin (Hb) levels and haematinics, while safety data included adverse drug reactions and safety laboratory variables.Results: Patients received a mean (range) cumulative dose of 1304 (100-3500) mg iron isomaltoside. Hb increased from 10.7(1.6) g/dL at baseline to 13.1(+/- 1.5) g/dL at the final visit. In addition, serum iron, ferritin and transferrin saturation increased and soluble transferrin receptor decreased. Calprotectin decreased, as did IBD symptom scores, Harvey-Bradshaw Index (Crohn's disease) and partial Mayo score (Ulcerative colitis). About 8% of patients reported transient adverse reactions, most commonly skin reactions, nausea and vomiting, and 2% SAEs, most frequently tachycardia.Conclusion: Iron isomaltoside was demonstrated to be effective and had a good safety profile in IBD patients in everyday clinical practice in Germany.