Once a patient requires hemodialysis, a physician who specializes in the kidney (nephrologist) will specify medications and different dialysis machine settings, such as time and duration of dialysis sessions. Dialysis patients typically dialyze 3 times a week for 3 - 4 hrs. This method of dialysis is usually performed in a clinical setting.

The principle of hemodialysis is the same as other methods of dialysis; it involves diffusion of solutes across a membrane. In contrast to peritoneal dialysis, in which transport is between fairly static fluid compartments, hemodialysis utilizes counter current flow, where the diasylate is flowing in the opposite direction to blood flow.

This maintains the concentration gradient across the membrane at a maximum, allowing the dialysis to be very efficient. As a result, hemodialysis can be performed intermittently (usually 3 times a week). Fluid removal (ultrafiltration) is achieved by altering the hydrostatic pressure of the blood compartment, causing free water to move across the membrane along a pressure gradient. The dialysis solution that is used is kept at body temperature and consists of a sterilized solution of mineral ions.

There are three primary modes of access to the blood in hemodialysis: an intravenous catheter, an arteriovenous fistula, or a graft. The type of access is influenced by factors such as the course of a patient's renal failure and the condition of his or her vasculature. Patients may have multiple accesses, usually because a fistula or graft is maturing, and a catheter is still being used.