Aims: Iron deficiency is common in patients with chronic kidney disease (CKD). Appropriate iron substitution is critical and intravenous iron is an established therapy for these patients. The objective of this study was to assess treatment routine, effectiveness, and safety of iron isomaltoside (Monofer (R), Pharmacosmos A/S, Holbaek, Denmark) in CKD patients in clinical practice. Materials and methods: This was a prospective observational study conducted in predialysis CKD patients treated with iron isomaltoside according to the product label and to routine clinical care. Results: The study included 108 patients with predialysis CKD: 22 were in stage 2 - 3, 41 in stage 4, and 45 in stage 5. The mean (standard deviation) age was 67 (15) years, and 55% of patients were male. The majority of patients (65%) received one iron isomaltoside treatment In patients with a baseline Hb amp;lt; 10 g/dL, the mean dose of iron isomaltoside in the study was lower than the estimated total iron requirement (567 mg versus 921 mg). A treatment response of Hb amp;gt;= 1 g/dL was achieved in 16/28 (57%) of patients, and the mean post-treatment Hb level was 10.5 g/dL. The probability of retreatment did not correlate with dose, but no dose administered was amp;gt; 1,000 mg. There were no serious adverse drug reactions. One nonserious adverse drug reaction - injection site discoloration - was reported, and the patient had an uneventful recovery. Conclusion: Iron isomaltoside shows a good effectiveness and safety profile in predialysis CKD patients. However, some patients did not receive adequate iron doses to allow for optimal correction of their iron deficiency anemia.