Acute renal replacement therapy (ARRT) is today routinely applied in critically ill patients with acute kidney injury. Nevertheless, differently from other therapies in the acute care setting which have specific posology, duration of treatment, serum through and peak levels and clearly predetermined continuous or intermittent way of administration, ARRT may appear difficult to dose, prescribe, deliver and monitor. Additionally, current literature has provided controversial results about many aspects of ARRT administration. This review will focus on the definition of dialytic dose, extensively detailing different dimensions of ARRT delivery: as a matter of fact, the provision of a dialytic session to a critically ill patient should not be limited to the simplistic mathematical calculation of an exact dose. Adequacy of ARRT implies the concomitant consideration of more complex issues such as timing, modality and techniques of ARRT delivery, anticoagulation and substitution fluids choice, membrane selection, monitor accuracy, the role of fluid overload and other patients' comorbidities. The capacity of clinicians of considering all these aspects, adapting the different dimensions of dose to the actual patients' needs, might be the fundamental missing element in the pathway towards significant outcome improvements of critically ill AKI patients needing ARRT.