[Skip to Content]


What Is Hemodialysis?

Our kidneys work like a garbage collection system. They clean extra fluid and waste from our blood. These wastes then leave the body as urine (pee).

If the kidneys stop working properly, waste can build up in the blood. That can get dangerous. So people with kidney failure need to filter out the waste.

Hemodialysis (pronounced: hee-mo-dye-AL-uh-sis) is a type of kidney dialysis. It's the one that doctors use most often to take over the kidneys' job of filtering the blood.

How Does it Work?

Hemodialysis uses a machine to pull blood out of the body, filter it, and pump the clean blood back into the body again. The actual filtering happens in a part of the machine called a dialyzer, or artificial kidney.

The dialyzer has two parts. One part is for blood. The other is filled with a cleaning solution called dialysate.

The two parts of the dialyzer are separated by a thin membrane. Blood cells and other important parts of the blood are too big to pass through the membrane. But waste products and extra fluids go through it easily.

The dialysate pulls waste and extra fluids out of the blood, through the membrane, and carries them away. The filtered blood is then pumped back to the body.

Blood flows from the body into the machine and back again through tubes. These tubes are attached to needles in the person's skin. The needles go into a large vein or artery through a vascular access. Doctors need to create this vascular access before dialysis can begin.

Creating a vascular access involves minor surgery. Most patients are awake during the procedure, but get a local anesthetic to stop feeling in the area. Surgeons usually create the vascular access a few weeks before hemodialysis starts. That way, the vascular access has time to heal.

There are three different kinds of vascular access, but they all do the same job:

When Does It Happen?

Hemodialysis usually takes about 4 hours and has to be done three times a week. Most people go to a special clinic — called a dialysis center — to get their treatments. Some people get treatments at a hospital. Occasionally, dialysis centers train families to do the treatments at home, but this isn't common.

After being hooked up to dialysis machines, patients lie down or sit in a chair. While the treatment is going on, they might use the time to read, watch TV, play videogames, or nap.

Are There Any Risks?

Some people feel the needles as they go into the vascular access. After that, dialysis treatments are painless.

Hemodialysis does have some risks, including:

Taking Care of Yourself During Hemodialysis

If you're doing hemodialysis, there are things you can do to stay healthy and avoid problems. Here are a few tips to help you take care of yourself:

Kidney dialysis is a treatment for kidney disease — it steps in to do the job of the kidneys and keep the body in balance. But it's not a cure. Dialysis alone won't heal a person's failing kidneys.

Some kinds of kidney disease get better and the person doesn't need dialysis anymore. Other people stop getting dialysis because they have a kidney transplant. But others need dialysis treatments for the rest of their lives. In these cases, people might switch back and forth between hemodialysis and another type of dialysis called peritoneal dialysis, which usually can be done at home.

Date reviewed: March 2015

Note: All information on TeensHealth® is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.

© 1995- The Nemours Foundation. All rights reserved.

Images provided by The Nemours Foundation, iStock, Getty Images, Corbis, Veer, Science Photo Library, Science Source Images, Shutterstock, and Clipart.com