Patient on haemodialysis with nurse

Haemodialysis: How does it work?

Haemodialysis cleans and filters your blood by using a machine to remove harmful wastes, excess salt, and water. Haemodialysis helps to control blood pressure and helps your body to keep the proper balance of important chemicals such as potassium, sodium, calcium and bicarbonate.1

Inside the haemodialysis machine there is a special filter called a dialyser. The dialyser functions as an artificial kidney. During treatment, your blood travels through a set of tubes into the dialyser that selectively filters out wastes and extra water, but not substances the body needs. Then, the cleaned blood flows through another set of tubes back into your body. The dialyser is connected to a machine that monitors blood flow and the amount of wastes in the blood as well as the amount of certain substances in the blood and in the haemodialysis fluid.1,2

To ensure sufficient cleaning of the blood, high blood flow is required. Therefore, the vessel from which the blood will be drawn is an important consideration. A small vessel would be inadequate. Additionally, it is wise to use a vessel with a strong wall, because the vessel will be punctured with a needle many times over several years. For these reasons, it is necessary to create a special access to the blood stream called a fistula, graft or catheter.2,3

Frequency of haemodialysis treatment

Haemodialysis is normally needed three times a week and is usually prepared, performed and monitored in a dialysis centre by nurses and trained technicians. Each treatment usually lasts from 3 to 5 or more hours. During treatment, you can read, write, sleep, talk, or watch TV.1

Another option is to perform dialysis treatment at home. You and a partner must go through intensive training in order to be able to prepare, perform, and monitor your treatment. Furthermore, the practicability of this treatment option depends on the technical capacity and spatial conditions in your home. The treatment schedule is similar to that within a dialysis centre: three times a week for 3 to 5 hours.1,2

frequent haemodialysis in detail
Haemodialysis: The blood flows out of the body and through a dialysing machine. After it has been cleaned of wastes in the dialyser, it flows back into a blood vessel.
Source: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)


  1. National Kidney Foundation (Accessed 14.2.19)
  2. Jameson, Fauci et al.: Harrison´s Principles of Internal Medicine, 20th Edition, McGraw Hill 2018
  3. National Kidney Foundation (Accessed 14.2.19)