In haemodialysis, blood is taken from an artery (often through a fistula joining an artery to a vein in the arm) and passed through a machine that contains a dialysis membrane and dialysis fluid. Heparin, an anticoagulation agent, is added to the blood. The blood is then returned to the body making sure that any bubbles are removed and do not enter the body.Haemodialysis is usually carried out about three times a week for several hours at home or in a clinic.