To demonstrate whether L-carnitine treatment could further improve the anemia in dialyzed patients under recombinant human erythropoietin (r-HuEPO) therapy, leading to a reduction in r-HuEPO requirements, L-carnitine (1 g intravenously after every dialysis session) was administered for 6 months to a group of 13 patients; the results were compared with data from a placebo control group (N = 11). Globular osmotic fragility and endogenous EPO secretion were also evaluated. L-Carnitine treatment promoted a 38.1% reduction in r-HuEPO requirements in the active group (102.2 +/- 52.6 U/kg/wk v 63.3 +/- 37.8 U/kg/wk; P < 0.02), with globular osmotic fragility and endogenous EPO levels remaining unchanged and thus not accounting for carnitine effect on anemia. In the active group, seven patients decreased r-HuEPO needs (responders), while six did not (nonresponders). Compared with nonresponders, responders showed higher mean values at time 0 for r-HuEPO requirements and endogenous plasma EPO levels, although not statistically significant. It is concluded that L-carnitine deficiency might promote EPO resistance in dialyzed patients, which is corrected by L-carnitine supplementation, ultimately reducing r-HuEPO requirements.