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What is haemodialysis?

Our kidneys usually filter and remove waste products and excess fluid from the blood. Haemodialysis is a way of replacing some of the functions of your kidney, if your kidneys have failed, by using a machine to filter and clean your blood.

Blood is pumped out of your body to the machine where it is passed through a series of tiny tubes, in an ‘artificial kidney’ or ‘dialyser’. The tubes are made of a special membrane that allows waste products and fluid to pass across it. Clear fluid called ‘dialysate’ is passed outside the tubes in the opposite direction. As the blood passes in one direction and the dialysate in the other, waste products and excess water pass into the dialysate,. which is then pumped out of the machine and the waste discarded down a drain, as your cleaned blood is pumped back into your body.

Your blood passes continuously through the dialyser during each dialysis session. Dialysis sessions normally last around four hours and take place three times a week; longer sessions are required for bigger people and for people who tend to gain more fluid between dialysis sessions. Shorter sessions may be used for small people, people whose kidneys are still working a bit, and people who have treatment more than three times a week.

Haemodialysis can be given in hospital, in free-standing dialysis units (often called satellite units), or at home. In hospital and satellite units, nurses and dialysis assistants help you with the treatment; home dialysis requires you or someone else to learn how to use the machine.

You may feel tired after the dialysis session, but as haemodialysis only takes place up to three times each week, the intervening days can allow you a certain amount of freedom to do normal activities, although restrictions in diet and fluid intake are usually necessary.


Haemodialysis machine

People are normally connected to the dialysis machine through two needles which are inserted into a ‘fistula’ or ‘graft’, usually in your arm. One needle takes your blood to the dialysis machine and the other needle brings back your cleaned blood.

A fistula (‘arteriovenous fistula is the full term) is a larger and stronger blood vessel in your arm or leg to make it easier to transfer your blood to and from the dialysis machine. It is created by connecting an artery to a vein by a small surgical operation. This is usually done in the forearm, but may be in the upper arm, in which case the surgeon may do this in two stages.

The fistula normally needs to be created around four to eight weeks before haemodialysis begins to allow time for the vein to increase in size .

If your blood vessels are too narrow you may be given an AV graft instead (where a piece of tubing is used to connect the artery to the vein). And sometimes, as a temporary measure or in an emergency, a small tube called a ‘catheter’  ‘neck line’, or ‘tunnelled line’ may be inserted into a vein in your neck or groin.

What to expect at a haemodialysis session

The thought of having needles inserted several times a week can be daunting. If you are concerned about this or scared of needles, an anaesthetic ointment can be applied instead a few hours before your dialysis session, or a local anaesthetic injection can be used to numb the area where the dialysis needles are inserted. The anaesthetic might ‘sting’ or ‘burn’ at first but this should only last a few seconds.

Once both needles are inserted, special tubing is attached to them, which is then connected to the dialysis machine.

You need to sit or lie down during your dialysis session but you can read, sleep or listen to the radio or watch programmes on your tablet or laptop  if you like. As you will be relatively still during the dialysis session, you may feel stiff at the end of the session.

You won’t feel like your blood is draining from you because the process ensures that the amount of blood in the machine and tubing remains minimal. However, some people can feel dizzy, tired and sick during and after their session. And some people say it is uncomfortable having a fistula in their arm or leg.

From time to time various blood tests are taken, and you may be asked to collect your urine to determine whether the frequency and duration of treatment are adequate and adjustments may be made on the basis of these measurements.

Haemodialysis and diet

Most people on haemodialysis need to adjust their diet. The major change in diet is usually a reduction in foods high in potassium, phosphate and sodium (salt). But a kidney dietitian will work with you to create a plan which is tailor-made to your needs and lifestyle.

One of the major restrictions that you may find difficult is your fluid intake, but reducing your salt intake may help you feel less thirsty. In the early stages of haemodialysis you may still pass some urine but, as time progresses the volume will decrease. In between dialysis sessions fluid tends to accumulate and if severe, shortness of breath can occur.

Urine measurements will be made from time to time to assess your fluid allowance, and how much dialysis you need. When and if changes are required, your dietician or kidney nurse will discuss these with you.

Medication and haemodialysis

Your kidney doctor may prescribe:

  • Vitamins and iron tablets and injections of a hormone called erythropoietin stimulating agent (ESA) or a tablet  to help your body make red blood cells
  • Tablets called phosphate binders to stop your body taking in too much phosphate from food and drink
  • Tablets to control blood pressure.

Haemodialysis and potential issues

You may be at increased risk of developing sepsis (blood poisoning). This is caused by bacteria entering the body and spreading through the blood, potentially leading to multiple organ failure. If you develop sepsis, you'll need to be admitted to hospital and treated with antibiotics.

Kidney dialysis patients are more at risk of chest and other infections and The Department of Health advises kidney dialysis patients to be vaccinated against pneumonia and hepatitis B as well as having an annual flu jab.

Other potential issues may include blockages in your fistula caused by blood clots and poor blood flow due to narrowing of blood vessels, but your medical team will be able to help you if these do occur.

Dialysis choices

Download our Dialysis Decision Aid to support you in making decisions about dialysis.

Reviewed April 2019

How will haemodialysis make me feel?

You may feel anxious, angry and upset about the upheaval to your personal, home, work and family life as you face the prospect of long-term haemodialysis and the restrictions associated with it.

This is all perfectly normal so talk to your kidney doctor or nurse about any concerns that may be affecting you physically and psychologically. They may also be able to put you in touch with other professionals, such as counsellors and social workers, who can help you with your mental wellbeing and give you information about benefits and other financial advice.

Take a look at our Dialysis Decision Aid booklet for more information about haemodialysis and other types of treatments generally available to people with kidney failure.

The booklet has space for your own notes and some suggested prompts to help you raise any issues that may be concerning you.

You can also find further advice and helpful tips in our How can I help myself? section.

Reviewed April 2019

Female with blonde hair, in a white lab coat and round black glasses in a research lab

"Having a device that is portable would allow more frequent dialysis over longer periods of time; this could drastically reduce the side effects of the treatment.”

Professor Grazia De Angelis

Researcher spotlight

Professor Grazia De Angelis, and her team at Edinburgh University, want to develop newer, improved options for kidney patients and believe that they have reached the final step in creating a workable, wearable kidney.  

Professor Grazia De Angelis and her team want to develop newer, improved options for kidney patients and believe that they have reached the final step in creating a workable, wearable kidney.  

The team in Edinburgh hope to have completed shortlisting the best materials in the next two years. From there, laboratory research will confirm the most effective material and the team will be ready to test it in a portable device. 

Our dialysis research

Our research is changing the lives for people living with kidney disease but more needs to be done.

Our life-saving research is only possible with your support.

Save lives.

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