Hemodialysis is not the same as dialysis, but it is the most common type of dialysis. Dialysis is the umbrella term for any treatment that filters waste and excess fluid from your blood when your kidneys can no longer do the job. Hemodialysis is one specific way of doing that. The other main type is peritoneal dialysis, which works through a completely different mechanism.
How Dialysis Types Are Related
Think of it this way: dialysis is the category, and hemodialysis is the most widely used option within it. Because hemodialysis is so common, people often use “dialysis” and “hemodialysis” interchangeably in casual conversation. That shorthand works fine in everyday life, but the distinction matters when you’re comparing treatment options or talking with a care team about what’s right for you.
The two primary forms of dialysis are hemodialysis and peritoneal dialysis. There’s also a specialized form called continuous renal replacement therapy (CRRT), which is used in intensive care units for patients who are too unstable for standard hemodialysis. About 75% of ICU patients needing kidney support receive CRRT rather than intermittent hemodialysis, because it removes fluid more gradually and is gentler on blood pressure.
How Hemodialysis Works
Hemodialysis uses a machine to pull blood out of your body, run it through an external filter called a dialyzer, and return the cleaned blood. The dialyzer is a plastic cartridge packed with thousands of tiny hollow fibers, each containing microscopic pores. Blood flows through these fibers at roughly 300 to 500 milliliters per minute while a sterile cleaning solution (dialysate) flows in the opposite direction on the outside of the fibers.
This counter-current flow is key. Waste products like excess potassium and phosphate naturally move from the blood (where concentrations are high) into the dialysate (where concentrations are low). At the same time, pressure differences pull excess water out of the blood. By continuously replacing the used dialysate with fresh solution, the machine keeps the concentration gradient steep so waste removal stays efficient throughout the session.
Standard in-center hemodialysis runs three times per week, with each session lasting about four hours. That adds up to roughly 12 to 13 hours of treatment per week. Some people do hemodialysis at home on a more frequent or flexible schedule, but the three-times-weekly center visit is the most common setup.
Vascular Access for Hemodialysis
Because hemodialysis moves large volumes of blood through an external circuit, you need a reliable access point in your bloodstream. The preferred option is an arteriovenous fistula, a surgical connection between an artery and a vein in your non-dominant arm. This causes the vein to enlarge and strengthen over several weeks, making it easier to insert needles for each session. If your blood vessels aren’t suitable for a fistula, a surgeon can place a synthetic graft between an artery and vein to serve the same purpose. In emergencies or when neither option is feasible, a catheter placed in a large vein (typically in the neck or chest) provides temporary or longer-term access.
How Peritoneal Dialysis Works
Peritoneal dialysis skips the external machine entirely. Instead, it uses the lining of your abdominal cavity, called the peritoneum, as a natural filter. A permanent catheter is placed into your abdomen through a small surgical procedure. You fill the abdominal cavity with a sterile dialysate solution, which draws waste products and excess fluid from the blood vessels in the peritoneal lining. After a set dwell time, you drain the used solution into a bag and replace it with fresh fluid.
There are two main approaches. Continuous ambulatory peritoneal dialysis involves about four manual exchanges spread throughout the day, each taking around 30 minutes. Continuous cyclic peritoneal dialysis uses a machine that performs exchanges automatically overnight for eight to nine hours while you sleep. Either way, peritoneal dialysis happens at home rather than in a clinic.
Practical Differences Between the Two
The biggest day-to-day difference is location and schedule. Hemodialysis typically means traveling to a dialysis center three days a week and sitting connected to a machine for four hours each visit. Peritoneal dialysis happens at home on your own schedule, which gives you more flexibility for work, travel, and daily routines. That said, peritoneal dialysis requires you to perform exchanges every day without exception, store supplies at home, and keep the catheter site clean to prevent infection.
Diet restrictions also differ. Hemodialysis patients generally face stricter limits on fluid intake and foods high in potassium, phosphorus, and sodium, because waste builds up between sessions. Peritoneal dialysis filters continuously or near-continuously, which allows a somewhat more relaxed diet for many people, though restrictions still apply.
Neither type is universally better. The choice depends on your kidney condition, overall health, lifestyle priorities, and the blood vessel or abdominal anatomy that makes one access route more practical than the other. Many people start with one type and switch to the other as their circumstances change.
Why the Terminology Confusion Exists
When someone says “I’m on dialysis,” they almost always mean hemodialysis. It accounts for the large majority of dialysis patients, and it’s the version most people picture: a chair in a clinic, tubing, a machine. Peritoneal dialysis is less visible because it happens privately at home. So in everyday language, “dialysis” has become shorthand for hemodialysis, even though the term technically includes both types. If you’re researching options or discussing care plans, knowing the distinction helps you ask sharper questions and understand what each path actually involves.