L-carnitine supplementation has been the subject of heated discussion in the context of the treatment of pediatric hemodialysis patients. The aim of this study was to analyze the effect of intravenous L-carnitine supplementation on the erythropoetin (EPO) requirement in six pediatric hemodialysis patients. All patients were on intravenous L-carnitine (2.5 g per session for patients >30 kg and 1 g for those <30 kg) for 9 months. The EPO dose was adapted monthly to maintain a target hemoglobin (Hb) level of 11-13 g/dl. Prior to the initiation of L-carnitine supplementation, the EPO requirement was 1.15 +/- 0.22 (range 0.37-1.75) microg/kg darbepoetin alpha. Free carnitine (FC) levels were measured before (40.4 +/- 4.9 micromol/l), immediately after the 9-month L-carnitine supplementation period (378.5 +/- 77.3 micromol/l), and 4 months after withdrawal of L-carnitine (95.6 +/- 4.0 micromol/l). After 9 months, the EPO dose was 0.47 +/- 0.10 microg/kg (p < 0.002). The Hb levels increased from 12.2 +/- 0.97 to 14.0 +/- 0.54 g/dl (p < 0.05) within the first 2 months, and the EPO dose was then decreased in a stepwise manner. In conclusion, following intravenous carnitine supplementation, FC levels were higher and persisted longer than expected. This rise was associated with increased Hb levels and decreased EPO requirement. Since controls were missing for this study, prospective long-term multi-center studies on a large number of patients are required to provide solid answers to the controversial question of L-carnitine supplementation in hemodialyzed children.