What happens during hemodialysis?

In hemodialysis, an artificial kidney removes waste from the blood. A surgeon must first create an "access," a place where blood can easily be taken from the body and sent to the artificial kidney for cleaning. The access, usually in the forearm, can be made from the patient's own blood vessels or from a piece of implanted tubing. The access is inside the body and cannot be seen from the outside. Usually, this surgery is done 2 to 3 months before dialysis starts so the body has time to heal.

Hemodialysis must be done 2 to 3 days per week, and lasts 3 to 5 hours each time. Blood travels through the artificial kidney, where waste products are filtered out, and the clean blood returns to the body. Only about 1/2 cup of blood is out of your body at any one time.
Jeanne Morrison, PhD
Family Medicine

Each hemodialysis treatment last about 3-4 hours and is done three times a week.  Time on the dialysis machine will depend on how well your kidneys function, how much weight you have gain, how much waste needs to be removed from your body, your body size and the type of artificial kidney you are using.  Your doctor will prescibed the necessary dialysis requirements and time. 

At the start of the dialysis treatment, the dialysis nurse will insert a needle into your fistula or graft.  The dialysis treatment is not painful.  Some patients may have a drop in blood pressure.  If this happens you may have cramps, vomit or feel sick to your stomach.   If you are dialysis in a treatment facility, continuous monitoring of  your dialysis session is being done by a trained professional.


There are two types of dialysis treatment: hemodialysis and peritoneal dialysis. Hemodialysis, the most common type, is usually administered at a center three times a week. Each treatment takes about three to four hours, sometimes longer. During treatment you may sit, read, sleep, watch television, or work on a laptop. Your blood and blood pressure are tested before and after each session, and you should be able to resume normal activities afterward. If needle insertion is painful for you, some anesthetic ointment or spray may be helpful. Hemodialysis can also be administered at home.

Continue Learning about Dialysis


Healthy kidneys remove waste from your blood and produce hormones your body needs. If your kidneys fail, you either need a kidney transplant or dialysis. Dialysis is a procedure that uses a machine to perform many of the functions ...

of the kidney. Dialysis can help prevent problems resulting from kidney failure and it allows people with kidney failure to live productive lives. Dialysis filters your blood, and like a health kidney, removes waste from your blood. Patients using dialysis are also required to follow a strict diet in order to stay healthy. There are two types of dialysis: hemodialysis and peritoneal dialysis. There are different advantages and disadvantages with both hemodialysis and peritoneal dialysis. Talk to your doctor about which type of dialysis would work better for you.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.