Dialysis is a procedure to remove waste products and excess fluid from the blood when the kidneys stop working properly. It often involves diverting blood to a machine to be cleaned.

Normally, the kidneys filter the blood, removing harmful waste products and excess fluid and turning these into urine to be passed out of the body.

  • Why do I need Dialysis?

    If your kidneys aren’t working properly, for example because you have advanced chronic kidney disease (kidney failure), the kidneys may not be able to clean the blood properly. Waste products and fluid can build up to dangerous levels in your body.

    Left untreated, this can cause a number of unpleasant symptoms and eventually be fatal. Dialysis filters out unwanted substances and fluids from the blood before this happens.

  • How is Dialysis performed?

    If your kidneys aren’t working properly, for example because you have advanced chronic kidney disease (kidney failure), the kidneys may not be able to clean the blood properly. Waste products and fluid can build up to dangerous levels in your body.

    Left untreated, this can cause a number of unpleasant symptoms and eventually be fatal. Dialysis filters out unwanted substances and fluids from the blood before this happens.

  • Preparing for treatment

    Before haemodialysis can start, you’ll usually need to have a special blood vessel created in your arm, called an arteriovenous fistula (AV fistula). This blood vessel is created by connecting an artery to a vein. Joining a vein and an artery together makes the blood vessel larger and stronger. This makes it easier to transfer your blood into the dialysis machine and back again. The operation to create the AV fistula is usually carried out around four to eight weeks before haemodialysis begins. This allows the tissue and skin surrounding the fistula to heal. If your blood vessels are too narrow to create an AV fistula, an alternative procedure known as an AV graft may be recommended. A piece of synthetic tubing (graft) is used to connect the artery to the vein.

  • The Haemodialysis process

    Most people need three sessions of haemodialysis a week, with each session lasting around four hours. This can be done in hospital, or at home if you’ve been trained to do it yourself.

    Two thin needles will be inserted into your AV fistula or graft and taped into place. One needle will slowly remove blood and transfer it to a machine called a dialyser or dialysis machine.

    The dialysis machine is made up of a series of membranes that act as filters and a special liquid called dialysate.

    The membranes filter waste products from your blood, which are passed into the dialysate fluid. The used dialysate fluid is pumped out of the dialyser and the filtered blood is passed back into your body through the second needle.

    During your dialysis sessions, you will sit or lie on a couch, recliner or bed. You will be able to read, listen to music, use your mobile phone or sleep.

    Haemodialysis isn’t painful, but some people feel a bit sick and dizzy, and may have muscle cramps during the procedure. This is caused by the rapid changes in blood fluid levels that occur during the treatment.

    After the dialysis session, the needles are removed and a plaster is applied to prevent bleeding. If you were treated in hospital, you can usually go home shortly afterwards.

    Fluid and diet restrictions

    If you’re having haemodialysis, the amount of fluid you can drink will be severely restricted.

    This is because the dialysis machine won’t be able to remove two to three days’ worth of excess fluid from your blood in four hours if you drink too much. This can lead to serious problems where excess fluid builds up in your blood, tissues and lungs.

    The amount of fluid you’re allowed to drink will depend on your size and weight. Most people are only allowed to drink 1,000-1,500ml (two to three pints) of fluid a day.

    You’ll also need to be careful what you eat while having haemodialysis because minerals such as sodium (salt), potassium and phosphorus that would normally be filtered out by your kidneys can build up to dangerous levels quickly between treatment sessions.

    You’ll be referred to a dietitian so a suitable diet plan can be drawn up for you. Diet plans differ from person to person, but it’s likely you’ll be asked to avoid eating foods high in potassium and phosphorus and to cut down the amount of salt you eat.


  • Peritoneal Dialysis

    There are two main types of peritoneal dialysis:

    • continuous ambulatory peritoneal dialysis (CAPD) – where your blood is filtered several times during the day

    • automated peritoneal dialysis (APD) – where a machine helps filter your blood during the night as you sleep Both treatments can be done at home once you’ve been trained to carry them out yourself. They’re described in more detail below.

    Preparing for treatment

    Before you can have CAPD or APD, an opening will need to be made in your abdomen. This will allow the dialysis fluid (dialysate) to be pumped into the space inside your abdomen (the peritoneal cavity). An incision is usually made just below your belly button. A thin tube called a catheter is inserted into the incision and the opening will normally be left to heal for a few weeks before treatment starts. The catheter is permanently attached to your abdomen, which some people find difficult. If you’re unable to get used to the catheter, you can have it removed and switch to haemodialysis instead.

    Continuous ambulatory peritoneal dialysis

    The equipment used to carry out CAPD consists of:

    • a bag containing dialysate fluid

    • an empty bag used to collect waste products

    • a series of tubing and clips used to secure both bags to the catheter

    • a wheeled stand that you can hang the bags from

    At first, the bag containing dialysate fluid is attached to the catheter in your abdomen. This allows the fluid to flow into the peritoneal cavity, where it’s left for a few hours.

    While the dialysate fluid is in the peritoneal cavity, waste products and excess fluid in the blood passing through the lining of the cavity are drawn out of the blood and into the fluid. A few hours later, the old fluid is drained into the waste bag. New fluid from a fresh bag is then passed into your peritoneal cavity to replace it, and left there until the next session. This process of exchanging the fluids is painless and usually takes about 30-40 minutes to complete.

    Exchanging the fluids isn’t painful, but you may find the sensation of filling your abdomen with fluid uncomfortable or strange at first. This should start to become less noticeable as you get used to it.

    Most people who use CAPD need to repeat this around four times a day. Between treatment sessions, the bags are disconnected and the end of the catheter is sealed.

    Automated peritoneal dialysis (APD)

    Automated peritoneal dialysis (APD) is similar to CAPD, except a machine is used to control the exchange of fluid while you sleep.

    You attach a bag filled with dialysate fluid to the APD machine before you go to bed. As you sleep, the machine automatically performs a number of fluid exchanges.

    You’ll usually need to be attached to the APD machine for 8-10 hours. At the end of the treatment session, some dialysate fluid will be left in your abdomen. This will be drained during your next session.

    During the night, an exchange can be temporarily interrupted if, for example, you need to get up to go to the toilet.

    Some people who have APD worry that a power cut or other technical problem could be dangerous. However, it is usually safe to miss one night’s worth of exchanges as long as you resume treatment within 24 hours. You’ll be given the telephone number of a 24-hour hotline you can call if you experience any technical problems.

    Fluid and diet restrictions

    If you’re having peritoneal dialysis, there are generally fewer restrictions on diet and fluid intake compared with haemodialysis because the treatment is carried out more often. However, you may sometimes be advised to limit how much fluid you drink and you may need to make some changes to your diet. A dietitian will discuss this with you if appropriate.

  • Risk and side effects of Dialysis

    Both Haemodialysis and Peritoneal Dialysis cause side effects. This is because of the way dialysis is carried out and the fact it can only partially compensate for the loss of kidney function.


    Fatigue, where you feel tired and exhausted all the time, is a common side effect in people who use either form of dialysis on a long-term basis. Fatigue is thought to be caused by a combination of the:

    • loss of normal kidney function

    • effects dialysis can have on the body

    • dietary restrictions associated with dialysis

    • overall stress and anxiety that many people with kidney failure experience

    You may want to talk to your dietitian to see if your diet can be adjusted to increase your energy levels.

    Regular exercise may also help. If you are fatigued and on dialysis, starting a programme of regular exercise can be difficult. But if you persevere, you will probably find that exercising becomes easier with time.

    Low-to-moderate aerobic exercise such as cycling, running, walking or swimming is best. Your GP or dialysis care team will be able to advise you about the type of exercise most suitable for you.

    Side effects of Haemodialysis

    Low Blood Pressure

    Low blood pressure (hypotension) is one of the most common side effects of haemodialysis. It can be caused by the drop in fluid levels during dialysis. Low blood pressure can cause nausea and dizziness.

    The best way to minimise these symptoms of low blood pressure is to keep to your daily fluid intake recommendations. If your symptoms persist, you should consult your dialysis care team because the amount of fluid used during dialysis may need to be adjusted.


    People receiving haemodialysis are at increased risk of developing sepsis (blood poisoning). This is where bacteria enter the body and spread through the blood, potentially leading to multiple organ failure.

    Warning symptoms include dizziness and a high temperature (fever) of 38C (100.4F) or above.

    If you have a high temperature, phone your dialysis unit immediately for advice. Alternatively, you can contact IRIS or your local out-of-hours service. If you develop sepsis, you’ll need to be admitted to hospital and treated with injections of antibiotics.

    Muscle cramps

    During haemodialysis, some people experience muscle cramps, usually in their lower legs. This is thought to be caused by the muscles reacting to the fluid loss that occurs during haemodialysis. Consult your dialysis care team if you have muscle cramps that become particularly painful. Medication may be available to help you cope with the symptoms.

    Itchy skin

    Many people receiving haemodialysis experience itchy skin, caused by a build-up of minerals in the body between dialysis sessions. Tell your care team if your skin becomes very itchy. They may recommend creams to soothe and moisturise your skin.

    Other side effects

    Other side effects of haemodialysis can include:

    • difficulties falling asleep (insomnia) or staying asleep

    • bone and joint pain

    • loss of libido (sex drive) and erectile dysfunction

    • dry mouth

    • anxiety

    Side effects of peritoneal Dialysis


    A common side effect of peritoneal dialysis is bacterial infection of the peritoneum (peritonitis). Peritonitis can occur if the dialysis equipment is not kept clean. If there are bacteria on the equipment, they can spread to the peritoneum (thin layer of tissue that lines the inside of the abdomen).

    The most effective way to prevent peritonitis is to keep your dialysis equipment clean. You’ll be given training in how to do this. Signs and symptoms of peritonitis can include:

    • abdominal pain

    • a high temperature (fever) of 38C (100.4F) or above

    • feeling and being sick

    • experiencing chills

    • the used dialysis fluid becoming cloudy

    Contact your dialysis unit immediately if you develop these symptoms. Alternatively, you can contact IRIS or your local out-of-hours service.

    Peritonitis is treated with injections of antibiotics. If the infection is severe or keeps coming back, you may need to switch to haemodialysis.


    People receiving peritoneal dialysis are at increased risk of developing a hernia because holding fluid inside the peritoneal cavity for many hours puts a strain on the muscles of the abdomen.

    The main symptom of a hernia is the appearance of a lump in your abdomen. The lump may be painless and may only be discovered during a check-up. In some people, certain activities, such as bending over or coughing, can cause the lump to appear.

    Surgery is usually needed to repair a hernia. During surgery, the surgeon will place the protruding tissue back inside your abdominal wall. The muscles of the abdominal wall may also be strengthened using a synthetic mesh.

    Weight gain

    The dialysate fluid used during peritoneal dialysis contains sugar molecules, some of which are absorbed into your body. This can increase your daily calorie consumption by up to several hundred calories a day.

    If you don’t compensate for these extra calories by reducing the amount of calories you eat and by taking regular exercise, it’s likely you will gain weight.

    If you’re concerned that you are gaining too much weight, you should talk to your dialysis team who can recommend a diet and exercise plan.

    Avoid following fad diets that claim to be able to help you lose a lot of weight quickly. This type of extreme dieting could upset your body’s chemistry and make you feel very ill.