Background: Intravenous iron supplementation is a basic principle in the therapy of haemodialysis (HD) patients with renal anaemia. In the Iron Dextran in Renal Anaemia (IDIRA) study, we analysed the efficacy of a therapy with low-molecular-weight iron dextran (LMW-ID) in stable HD patients with adequate iron stores previously treated with ferric gluconate. Methods: IDIRA was an open-label, prospective, non-randomized, observational multicenter trial over 12 months in iron-repleted HD patients. All patients were treated with intravenous LMW-ID. Measures of efficacy were changes of haemoglobin (Hb), serum ferritin, erythropoietin dose and the response to iron therapy calculated as ferritin efficacy and Hb efficacy. Statistical analysis was done by the Wilcoxon test. Results: A total of 221 HD patients with a mean age 63.7 ± 13.8 years were included. A total of 208 out of 221 patients were on erythropoietin therapy. Median time on dialysis was 2 (1–4) years. Mean Kt/V was 1.3. Of the 221 patients, 208 completed the 12-month study period. Mean Hb and serum ferritin increased without the need for higher erythropoietin doses. The mean amount of iron per week administered remained stable. Ferritin efficacy and Hb efficacy improved using LMW-ID (p < 0.01). Conclusions: We conclude that LMW-ID improves anaemia management even in iron-pretreated HD patients.