The efficacy of ESA biosimilars has been tested mainly in the few studies needed for marketing authorization,1-5 whereas data from individual self-reported clinical experience are lacking. Such information, together with pharmacovigilance data, is key to obtaining reassurance regarding the safety of these products. Of note, 2 studies of efficacy when switching from originator to biosimilar in hemodialysis patients have reported a dosing penalty (ie, requiring higher doses to maintain Hb level) of 4% to 13% for HX575 (epoetin alfa; Binocrit) and 10% to 15% for SB309 (epoetin zeta; Retacrit).