How long haemodialysis takes and how often it is needed

Each dialysis session usually lasts 3-4 hours and is normally done during the day. Most children have sessions three times a week, though they may need it more often. . 

Although children are connected to the machine, they can read, do school work, play with toys or sleep.

Where haemodialysis takes place


Most of the time, haemodialysis takes place in a special area in the paediatric renal unit at hospital (hospital HD).

Your unit can offer transport, such as a taxi or bus service, so your child can travel to and from the hospital. 


Some children have haemodialysis in their home (home HD). In the UK there are now two types of HD machines. The one that is most commonly available is about the size of a large chest of drawers and heavy. These machines will require some modifications to your home in order to work safely and effectively. There is also a smaller, mobile machine that does not require any home modifications but you will require more space at home to store all the supplies. Both types of HD service may not be available at your unit, but if you ask your consultant, arrangements can be made for you to learn at another unit. 

In order to do undertake HD at home, some practical issues will need to be thought about.

  • Your home will need to be able to fit and accommodate the equipment. The machines and equipment, including the supplies of concentrate and water, need to be carefully stored away from children and pets.
  • Your unit will assess your child. Some children who are very young or small may only be suitable for hospital HD.

If you decide to use haemodialysis at home, you will receive lots of training and support from your unit. 

How dialysis works

For each dialysis session your child is connected to the haemodialysis machine. 

Before dialysis

Your child will need a quick assessment before each session. The machine is then programmed especially for your child. 

If at the hospital, a haemodialysis nurse will do these tests and set up the machine. If at home, you or another carer who has been trained will do this. The tests include:

  • weight – to estimate how much fluid needs to be removed in the dialysis session
  • blood pressure measurement (blood pressure medicines are usually not taken on the morning before dialysis)
  • temperature – to make sure your child is not too hot or cold.

During dialysis

  • Your child is connected to the machine. If he or she has a fistula, one or two needles are inserted into it – special gel or cream can be used to help your child stop feeling any pain. The needle(s) are placed in the fistula each dialysis session. If your child has a line, the tubes will be connected to the port(s) at the end of the catheter.
  • The machine pumps blood out of the body through the tube. The blood passes into an artificial kidney, which is called a dialyser. This sits outside the machine.
  • The dialyser has a membrane that contains millions of small holes that acts as a sieve or filter – this works a bit like the filters in our kidneys (the glomeruli). The dialyser is continuously bathed with a special fluid called dialysate
  • As blood passes through the dialyser, waste products and salts move across the dialyser membrane into the dialysate fluid and are safely removed from the body. 
  • Excess water also filters out of the blood through the membrane and is removed from the body. This is called ultrafiltration.
  • The cleaned blood is then pumped back out of the dialyser through another tube and back into the body. 

Blood is pumped out of and into the body quickly – only a small amount of blood is outside the body at any time.

A nurse – or you if at home – will measure your child’s blood pressure throughout the session.

Although your child is connected to the machine, he or she can read books, play games, do homework or sleep.

A newer type of ‘haemodialysis’ called haemodiafiltration (HDF) is performed in some children’s kidney units. It uses a similar machine but works differently to clean out the blood and remove more toxins from it. 


Your child may receive some of his or her medicines at the same time as haemodialysis. These are added to the circuit.

  • Iron supplements – some children need these for anaemia, a common problem in the blood of children with chronic kidney disease; iron helps the body make healthy red blood cells to carry oxygen round the body
  • EPO (erythropoietin) or darbepoietin – many children need to take this hormone as a medicine, as their kidneys are less able to make the hormone, which also helps make red blood cells.

After the dialysis session

After the session, your child is disconnected from the machine. The nurse – or you, if at home – will take your child’s blood pressure and temperature, and weigh him or her to check that the right amount of fluid has been removed.