Dialysis is a mechanical process that performs the work of healthy kidneys. Hemodialysis uses a man-made membrane (dialyzer) to remove wastes and extra fluid from the blood. It also restores the proper balance of certain minerals in the blood (electrolytes). The fluid used to filter or clean the blood is called dialysate. Hemodialysis is usually done in a hospital or dialysis center.

Before dialysis can begin, the doctor has to create a dialysis access. In hemodialysis, the access is the place where the dialysis needles are inserted, to carry the blood to and from the dialysis machine. For the best access, the doctor builds a connection, called a fistula, between an artery and a vein in the forearm. Or the doctor uses a tube called a graft to connect the artery and a vein. Sometimes a plastic tube (central venous catheter) is placed in the neck.