Assessment of hemodialysis adequacy may require different approaches for the stable, outpatient with end-stage renal disease (ESRD) and for the sick, inpatient with acute kidney injury (AKI). Variability of urea distribution volume, urea generation, and treatment schedule, for instance, complicates dialysis dosing in the latter group although progress has been made in our understanding of their needs. There is a third population, however, for whom hemodialysis dosing requirements remain unclear—the hospitalized ESRD patient. This commentary discusses the key urea kinetic differences between stable ESRD and AKI to give the context to where, on the intervening spectrum, the hospitalized ESRD patient might lie. The limited literature examining hemodialysis dosing in this population is discussed along with those outstanding questions that might form the basis of a future research agenda.