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 long will I need dialysis for?

It depends. In some cases, kidney failure may be a temporary problem and dialysis can be stopped when your kidneys recover.

But often, someone with kidney failure will need a kidney transplant. It's not always possible to carry out a kidney transplant straight away, so dialysis may be needed until a suitable donor kidney becomes available.

If a kidney transplant isn't suitable for you, for example because you're not well enough to have a major operation, dialysis may be needed for the rest of your life.

What happens during dialysis

There are 2 main types of dialysis: haemodialysis and peritoneal dialysis.


Haemodialysis is the most common type of dialysis and the one most people are aware of.

During the procedure, a tube is attached to a needle in your arm. Blood passes along the tube and into an external machine that filters it, before it's passed back into the arm along another tube.

This is usually carried out 3 days a week, with each session lasting around 4 hours.

Peritoneal dialysis

Peritoneal dialysis uses the inside lining of your abdomen (the peritoneum) as the filter, rather than a machine. Like the kidneys, the peritoneum contains thousands of tiny blood vessels, making it a useful filtering device.

Before treatment starts, an incision is made near your belly button and a thin tube called a catheter is inserted through the incision and into the space inside your abdomen (the peritoneal cavity). This is left in place permanently.

Fluid is pumped into the peritoneal cavity through the catheter. As blood passes through the blood vessels lining the peritoneal cavity, waste products and excess fluid are drawn out of the blood and into the dialysis fluid. The used fluid is drained into a bag a few hours later and replaced with fresh fluid.

Changing the fluid usually takes about 30-40 minutes and normally needs to be repeated around 4 times a day. If you prefer, this can be done by a machine overnight while you sleep.  

Which type of dialysis is best?

In many cases, you'll be able to choose which type of dialysis you want to have.

The 2 techniques are equally effective for most people, but each has its own advantages and drawbacks. For example:

  • haemodialysis means you'll have 4 treatment-free days a week, but the treatment sessions last longer and you may need to visit hospital each time
  • peritoneal dialysis can be done quite easily at home and can sometimes be done while you sleep, but it needs to be done every day

If you're able to choose the type of dialysis you prefer, your care team will discuss the pros and cons of each option with you to help you make a decision.

Side effects of dialysis

Haemodialysis can cause itchy skin and muscle cramps. Peritoneal dialysis can put you at risk of developing peritonitis (infection of the thin membrane that surrounds your abdomen).

Both types of dialysis can make you feel exhausted.

Life on dialysis

Many people on dialysis have a good quality of life. If you're otherwise well, you should be able to:

  • continue working or studying
  • drive
  • exercise
  • go swimming
  • go on holiday

Most people can remain on dialysis for many years, although the treatment can only partially compensate for the loss of kidney function and having kidneys that don't work properly can place a significant strain on the body.

Sadly, this means that people can die while on dialysis if they don't have a kidney transplant, particularly elderly people and those with other health problems. Someone who starts dialysis in their late 20s can expect to live for up to 20 years or longer, but adults over 75 may only survive for 2 to 3 years.

However, it's important to be aware that survival rates of people on dialysis have improved over the past decade and are expected to continue improving in the future.

How it's performed

There are 2 main types of dialysis: haemodialysis and peritoneal dialysis.

  • Haemodialysis involves diverting blood into an external machine, where it's filtered before being returned to the body
  • Peritoneal dialysis involves pumping dialysis fluid into the space inside your abdomen (tummy) to draw out waste products from the blood passing through vessels lining the inside of the abdomen

These 2 treatments are outlined in more detail below.


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 4 to 8 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.

As a short-term measure, or in an emergency, you may be given a neck line. This is where a small tube is inserted into a vein in your neck.

The haemodialysis process

Most people need 3 sessions of haemodialysis a week, with each session lasting around 4 hours. This can be done in hospital, or at home if you've been trained to do it yourself.

2 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 2 to 3 days' worth of excess fluid from your blood in 4 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 (2 to 3 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 2 main types of peritoneal dialysis:

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 4 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.

Dialysis and pregnancy

Becoming pregnant while on dialysis can sometimes be dangerous for the mother and baby.

It's possible to have a successful pregnancy while on dialysis, but you'll probably need to be monitored more closely at a dialysis unit and you may need more frequent or longer treatment sessions.

If you're considering trying for a baby, it's a good idea to discuss this with your doctor first. 

Dialysis equipment

If you're having home haemodialysis or peritoneal dialysis, the supplies and equipment you need will normally be provided by your hospital or dialysis clinic.

You'll be told how to get and store your supplies as part of your training in carrying out the procedure.

It's important to make sure you have enough supplies of equipment in case of an emergency, such as adverse weather conditions that prevent you from obtaining supplies. Your doctor or nurse may suggest keeping at least a week's worth of equipment as an emergency backup supply.

You should also let your electrical company know if you're using home haemodialysis or automated peritoneal dialysis. This is so they can treat you as a priority in the event that your electrical supply is disrupted.

Pros and cons of the two types

If dialysis is recommended for you, you'll often be able to choose whether to have haemodialysis or peritoneal dialysis.

Both methods of dialysis are equally effective for most people, so it's usually a case of personal preference.

However, there may be some situations where a particular type of dialysis is best. For example, peritoneal dialysis may be recommended for:

  • children aged 2 or younger
  • people who still have some limited kidney function
  • adults who don't have other serious health conditions, such as heart disease or cancer

Haemodialysis may be recommended for people who are unable to carry out peritoneal dialysis themselves, such as those who are visually impaired, have dementia or are in a poor state of health.

Any decision you make about which procedure to have will not be final. It's possible to move from one to the other. You can read about some of the main advantages and disadvantages of each technique below.


The main advantage of haemodialysis is that you have 4 dialysis-free days a week.

The procedure usually involves using a dialysis machine 3 times a week, with each session usually lasting about 4 hours. You'll need to plan your life around these sessions.

The sessions are often carried out in a dialysis clinic, so you may need to travel regularly for treatment. However, it may be possible to be trained how to use the equipment at home.

If you travel to another country, you'll have to arrange access to dialysis facilities beforehand. Inform the staff at your dialysis centre well in advance as they may be able to arrange for you to be referred to a dialysis unit at your destination. 

Another disadvantage of haemodialysis is that your diet and the amount of fluid you drink needs to be restricted. Many people receiving haemodialysis have to avoid certain foods and are usually advised not to drink more than a couple of cups of fluid a day.

Peritoneal dialysis

Unlike haemodialysis, the obvious advantage of peritoneal dialysis is that regular visits to a dialysis unit aren't required and it can be carried out at home without needing any bulky haemodialysis equipment.

The equipment used for peritoneal dialysis is much more portable, so you have more freedom to travel than you would if having haemodialysis.

There are also fewer restrictions on diet and fluid intake for people having peritoneal dialysis, compared to those having haemodialysis.

One of the main disadvantages of peritoneal dialysis is that it needs to be carried out every day, which you may find very disruptive. You may also find it upsetting to have a thin tube (catheter) left permanently in your abdomen (tummy), although it can often be concealed under clothing.

Another major disadvantage of peritoneal dialysis is that you're at risk of developing peritonitis (infection of the thin membrane that lines your abdomen). In rare cases, your peritoneum may gradually become thickened and scarred. Some people may need to switch to haemodialysis after a few years to stop this happening.

Another drawback of peritoneal dialysis is that the dialysis fluid used can cause a reduction in protein levels, which can lead to a lack of energy and, in some cases, malnutrition. Weight gain is also a possible side effect.

Continuous versus automated peritoneal dialysis

If you choose to have peritoneal dialysis, you will have to decide whether you want to have continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD).

The main advantage of CAPD is that the equipment is portable. This gives you more freedom to travel away from your house. For example, you may be able to take your CAPD equipment to your workplace. However, you will need to spend at least 2 hours a day performing dialysis.

The main advantage of using APD is that your days are dialysis-free. However, you need to keep and maintain a dialysis machine (and the associated equipment) in your house, which doesn't suit some people. 

Risks and side effects

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 the NHS 24 111 service 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:

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 NHS 24 111 service 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.

Last updated:
25 January 2023