Glycosylation is one of the most critical factors affecting the quality, the safety and the potency of recombinant erythropoietin. Small changes during production can significantly affect glycosylation, and so the potency, of recombinant erythropoietin. Due to patent expirations, we expect biosimilar erythropoietins to play an increasing role in healthcare in coming years. Governmental regulatory agencies and biopharmaceutical companies therefore have an urgent need for reliable methods that can accurately characterize and evaluate these biological products, particularly in terms of their glycosylation. In this review, we provide an overview of current analytical tools for qualitative and quantitative analysis of erythropoietin glycosylation. (C) 2015 Elsevier B.V. All rights reserved.