How Does a Hemodialysis Machine Work?

Whether you do home hemodialysis or in-center hemodialysis, you’ll rely on a hemodialysis machine to filter your blood. The machine filters your blood through a dialyzer, also known as an artificial kidney, with built-in safety checks to be sure the process is safe and effective. Home and in-center hemodialysis machines are very similar in function, though the home machine is much smaller.

What does a dialysis machine do?

Here’s a basic overview of a hemodialysis machine’s parts and functions:
How does a hemodialysis machine work?

  1. Two tubes are connected via your hemodialysis access. Blood flows from your body into the machine through 1 of the tubes. 
  2. If your doctor prescribes blood thinner as part of your treatment, it will be added to keep your blood from clotting while it’s in the machine. 
  3. A pressure monitor and pump work together to keep the flow at the right rate. 
  4. Your blood enters the dialyzer, where it is filtered. 
  5. Dialysate solution enters the dialyzer. It draws the waste out of your blood. 
  6. Used dialysate solution is pumped out of the machine and discarded. 
  7. Your blood goes through another pressure monitor and an air trap to make sure it’s safe to go back into your body. 
  8. Your cleaned blood returns to your body through the second tube attached to your access site.

What is dialysate?

Dialysate is a fluid that is made up of water, electrolytes and salts. During dialysis, dialysate helps to clean your blood inside the dialyzer by removing waste products and balancing electrolytes. Your nephrologist will prescribe the dialysate that is right for your body’s needs. 

What does a dialyzer (artificial kidney) do? 

A dialyzer is the part in the hemodialysis machine where your blood gets filtered.
Power failure during dialysis.
  • The core of the dialyzer is made up of thousands of tiny mesh tubes.
  • Your blood flows inside each tube, and the dialysate stays on the outside of the tubes.
  • Tiny pores in the tubes let waste and excess fluids pass from your blood into the dialysate.
  • Your cleaned blood then leaves the dialyzer and is returned to your body.

How is my dialysis treatment monitored? 

During your dialysis session, detailed information will show on the machine’s monitoring screen. Every function will be monitored, including the pump speed, blood pressure and dialysate temperature. Every check is designed to make sure your dialysis session is safe and effective.

An alert will sound if anything needs attention. An alert may simply mean the machine needs to be checked or something needs to be adjusted. If you’re doing home hemodialysis, you’ll be trained on what to do for any alert you might hear as part of your overall dialysis and safety training. You can also call your nurse 24/7 if you have questions or need assistance. If you receive in-center hemodialysis, your care team will monitor the machine throughout the process and make any adjustments necessary.

Your treatment will also be monitored through your personal Fresenius Kidney Care Portal. If you’re on home dialysis, you’ll log your daily treatment data for instant delivery to your care team. You’ll also be able to view lab results, track your supply order and communicate with your care team about any issues or concerns.

What happens if there’s a power failure during dialysis?

PD Support
If the power goes off while your cycler is working, it will automatically close all the lines. The machine will store the information about your session using a backup battery. If the power comes back on soon, that stored information lets the machine continue the session. If not, it’s best to call your home dialysis nurse about what to do next—support is available 24/7 if you ever have questions or concerns.


Learn how to feel your best and thrive on dialysis. Choose the class format that fits your life—educator-led or self-guided.
Sign Up now
Dialysate and blood don’t mix.


Only waste products and water pass from your blood into the dialysis solution.


During a typical dialysis treatment, only a pint of blood is outside of your body being cleaned and returned at any time. One pint is the same amount of blood you give during a donation.


Home hemodialysis machines function similarly to in-center machines, though they’re much smaller and easy to handle. Some home machines can fit on a nightstand—or you can take it with you when you travel. 


Register with your local power company to get on their medical priority list. Letting your provider know that you use electricity for home dialysis can help you get your power restored faster.