Erythropoietin (EPO) is α-glycoprotein hormone of 165 amino acids. EPO is mainly produced by renal peritubular interstitial cells in the kidney. The human EPO gene was cloned in 1983, allowing for clinical development of recombinant human EPO (rhEPO). EPO is used in the treatment of severe anemia. EPO has low stability and degraded in aqueous solution. It stabilized commercially using human serum albumin (HSA); however, HSA is restricted to be used as pharmaceutical additives in Europe. In addition, many attempts have been made to resolve the problems associated with the repetitive injections of EPO; these attempts have been made to formulate EPO in microspheres. Generally, nanoparticles exhibit better in vivo performance over microparticles regarding to the cellular uptake and the bio-distribution. This book provides full detailed information about the stability of biopharmaceuticals. It shows different EPO formula that is free from HSA and the different methods that can be used to monitor the stability of EPO. Finally, the method to formulate EPO in nanoparticles is clearly described here. This book considered a useful source for people working in biopharmaceutical formulation.