How Does Dialysis Work?

You probably never think about your kidneys cleaning your blood — they just get on with it, around the clock, filtering out waste and extra fluid and sending them on their way as urine. Dialysis enters the picture when kidneys can no longer do enough of that work themselves. It doesn't heal the kidneys, and it doesn't do everything they did. What it does is take over the cleaning part, well enough to keep waste and fluid from building up to dangerous levels.

The short introduction video at the top of this page, which runs for about a minute and a half, walks through haemodialysis, the best-known form. But there are actually two quite different routes to the same goal, and comparing them is the easiest way to understand what dialysis really is.

Haemodialysis: the blood takes a trip outside the body

In haemodialysis, blood leaves the body through a needle placed in a specially prepared blood vessel, usually in the arm, and travels through a machine. Inside that machine sits a filter — sometimes called an artificial kidney — where the blood passes alongside a special fluid, separated by a thin membrane. Waste and extra water move across the membrane into the fluid, and the cleaned blood returns to the body. A session typically takes a few hours and is usually done at a dialysis centre, several times a week, with the care team running the machine and watching over you while it works.

Peritoneal dialysis: the filter is already inside you

Peritoneal dialysis skips the machine-as-filter idea entirely. Instead, it uses the peritoneum — the natural lining of your abdomen — as the membrane. A soft tube placed in the abdomen lets a special fluid flow in and sit there for a while; as it sits, waste and extra fluid from nearby blood vessels pass into it, and then the fluid is drained away and replaced with fresh. The site's separate video on peritoneal dialysis for kidney disease shows this gentler, more continuous approach, which many people do at home, either in exchanges during the day or with a small machine helping overnight.

Same destination, different daily life

Set side by side, the contrast is mostly about where and when. Haemodialysis concentrates the work into set sessions at a centre, handled by staff, with days off in between. Peritoneal dialysis spreads the work out — more frequent, often daily, but done by you at home and built around your routine rather than a centre's timetable. Both need a planned access point created ahead of time, both come with dietary and fluid guidance from your team, and neither is a cure: they're treatments that replace part of kidney function for as long as they're needed. Which one suits a person depends on their health, their veins and abdomen, their home situation, and their own preference — a conversation kidney specialists have carefully with each patient, because kidneys connect to so much else. If you're curious how kidney problems first show themselves, our guide to kidney stones and how they're treated covers the far more common problem most people meet first.

One thing both forms share: starting dialysis is a major life change, and tiredness, mood, and appetite can all shift as the body adjusts. Good dialysis care is a team effort — nurses, dietitians, and your kidney doctor adjusting the prescription over time — not just a machine or a bag of fluid doing a mechanical job.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician, researcher, and former Duke faculty.

Educational only — this article is general information about dialysis, not medical advice. Decisions about whether and when to start dialysis, and which type, belong with your own kidney specialist, who knows your blood tests, overall health, and circumstances.

Frequently Asked Questions

Does dialysis cure kidney failure?
No. Dialysis replaces part of what healthy kidneys do — removing waste and extra fluid — but it doesn't repair the kidneys themselves. For some people a kidney transplant is an option that their team may discuss; others continue on dialysis long term.

Does dialysis hurt?
The treatment itself is generally not described as painful, though the needles used for haemodialysis access can cause brief discomfort, and cramps or a drop in blood pressure can happen during sessions. With peritoneal dialysis, the draining and filling can feel unusual at first. Your team can usually adjust things if a session feels difficult — tell them rather than putting up with it.

Can you live a normal life on dialysis?
Many people work, travel, and carry on with much of daily life while on dialysis, though it takes planning around sessions or exchanges, and energy levels vary. How someone feels depends on their overall health as much as on the dialysis itself, which is why follow-up with the kidney team matters.