Iron deficiency, without anaemia, is common in the general population and induces various symptoms. Its management consists of oral and intravenous supplementation for cases of inefficacy of or intolerance to oral iron. We assessed the efficacy of intravenous iron therapy in non-anaemic iron-deficient patients with fatigue. We prospectively evaluated the level of fatigue, using the Fatigue Severity Scale (FSS), in patients suffering from iron deficiency without anaemia, treated by intravenous iron at the moment of the perfusion (W0), after 4 weeks (W4), and 12 weeks (W12). Of 25 patients, at W0, the mean FFS was 49.3+/-13.7. There was a significant improvement in FSS at W4 (44+/-15; p = 0.01) and a sustained response at W12 with an FFS of 35.8+/-17.1 (p < 0,0001). There was no correlation between FSS and serum ferritin level at W12 (p=0.54) or between serum ferritin at W12 and difference between FSS at W0 and W12 (p=0.58). There were six mild adverse events (24%): asthenia (8%), nausea (8%), headache (4%), local pain (4%); and no serious adverse events. Our results suggest the rapid efficacy of intravenous iron in improving fatigue in iron deficiency without anaemia with a good profile of tolerance.