The focus of this chapter is on four recombinant growth factor products (erythropoietins, G‐CSF, KGF, and thrombopoietins) and three hormone products (glucagon,somatropin, and pegvisomant). We compiled the information related to drug interactions found in scientific publications and regulatory agency approved labeling documents. We reference U.S. prescribing information (PI) from the Drugs@FDA website and European summary of product characteristics (SPC) from the European Medicines Agency (EMA)'s website for European public assessment reports (EPARs). In addition, we gathered information from manufacturers and other interest groups that also post up‐to‐date labeling documents on their product websites.