Hemodialysis filters your blood through a machine that does the work your kidneys can no longer handle: removing waste, excess fluid, and balancing electrolytes. The standard schedule is three sessions per week, each lasting four to five hours, typically at a dialysis center. The process requires surgical access to your bloodstream, a specialized filter, and close monitoring throughout every session.
How the Machine Filters Your Blood
At the core of every hemodialysis machine is a component called a dialyzer, sometimes referred to as an artificial kidney. Inside it, your blood flows on one side of a thin semipermeable membrane while a cleansing fluid called dialysate flows on the other side. Waste products like urea and creatinine move from your blood (where concentrations are high) across the membrane into the dialysate (where concentrations are low). This process, called diffusion, is the same principle that makes a tea bag release flavor into hot water.
At the same time, the machine uses pressure differences across the membrane to pull excess fluid out of your blood. This is the ultrafiltration component. The rate of fluid removal is set by your dialysis team based on how much fluid weight you’ve gained between sessions. If too much fluid is pulled too quickly, your blood pressure can drop and you may experience cramping. In cases where you’ve gained a lot of fluid weight, the session may need to run longer, or you may need an extra treatment day to remove it safely.
Getting Access to Your Bloodstream
Before hemodialysis can begin, you need a reliable way to move blood out of your body, through the machine, and back again. This requires a minor surgery to create what’s called vascular access. There are three main types, and the one you get matters for your long-term comfort and safety.
- AV fistula: A surgeon connects an artery directly to a vein in your arm. This is considered the best option because it lasts the longest and carries the lowest risk of infection and clotting. It does need time to mature before it can be used.
- AV graft: A soft synthetic tube joins an artery and vein in your arm. This option is used when your veins aren’t suitable for a fistula. It can typically be used sooner, but it’s more prone to complications over time.
- Central venous catheter: A soft tube placed into a large vein, usually in the neck. Catheters are generally temporary, used while a fistula or graft is healing, though some people end up using them permanently. They carry the highest infection risk of the three options.
What a Typical Session Looks Like
When you arrive at the dialysis center, a technician or nurse checks your weight and blood pressure. The weight check is important because it tells the team how much fluid has built up since your last visit. Two needles are inserted into your access site (or your catheter is connected), and blood begins flowing through tubing into the dialyzer. One line carries blood out, the other returns cleaned blood to your body.
During the four to five hours you’re connected, you can read, sleep, watch television, or work on a laptop. The machine continuously monitors several safety parameters. It tracks venous and arterial pressure in the blood circuit and watches for any air bubbles in the lines. If something falls outside a safe range, the machine triggers an alarm and pauses or adjusts the process. Staff are present throughout to respond.
After the session, your needles are removed, the access site is checked, and your weight and blood pressure are measured again to confirm the right amount of fluid was removed.
Common Side Effects During and After Treatment
The most frequent symptoms during hemodialysis are muscle cramps, nausea, vomiting, and headaches. These are far more common than serious complications, but they can be significant enough to affect quality of life. Some people feel drained or “washed out” for hours after a session, which can make it hard to maintain a normal schedule on treatment days.
These side effects sometimes lead people to cut sessions short or skip them altogether. That’s a real problem: incomplete treatments allow waste and fluid to accumulate, which raises the risk of hospitalization. If you’re consistently struggling with symptoms, your care team can adjust the treatment speed, fluid removal rate, or session length to make it more tolerable.
Diet and Fluid Changes
Hemodialysis doesn’t run 24/7 the way healthy kidneys do, so what you eat and drink between sessions directly affects how you feel during treatment. You’ll work with a renal dietitian to create an eating plan tailored to your lab results and health needs. The specifics vary from person to person, but certain patterns apply broadly.
Potassium, found in foods like bananas, potatoes, and oranges, needs to be managed carefully because your kidneys can no longer regulate it between sessions. High potassium levels can cause dangerous heart rhythm problems. Phosphorus, found in dairy, nuts, and processed foods, also builds up and can weaken bones over time. Most people on hemodialysis are limited to about half a cup of milk per day, for example, and many take phosphorus-binding medications with meals.
Protein needs actually increase on hemodialysis because the process itself removes some protein from your blood. A typical serving of meat is about three ounces, roughly the size of your palm or a deck of cards, and your dietitian will recommend a specific number of servings per day. Fluid intake also needs to be restricted, since excess fluid between sessions means more aggressive removal during treatment, which increases the chance of cramping and low blood pressure.
Home Hemodialysis as an Alternative
Not everyone needs to go to a center three times a week. Home hemodialysis lets you perform treatments in your own space, often on a more flexible schedule. Some home programs use shorter, more frequent sessions, running 1.5 to 2.5 hours five to six times per week. Others use longer nocturnal sessions of six to eight hours while you sleep, three to six nights per week.
More frequent dialysis more closely mimics how real kidneys work: filtering continuously rather than in big bursts. This approach can allow a more relaxed diet and fluid intake, since waste and fluid don’t build up as much between sessions. Home dialysis does require training (usually several weeks), a care partner in many programs, and space for equipment and supplies. It’s not right for everyone, but it offers significantly more control over your schedule.
Long-Term Outlook
Hemodialysis is a life-sustaining treatment, but it isn’t a cure. According to the most recent data from the U.S. Renal Data System, five-year survival for people who started hemodialysis in 2019 was about 41%. That number hasn’t changed much over the past decade, and it varies significantly by age, with younger patients generally doing better than older ones.
These numbers reflect the reality that most people starting dialysis already have other serious health conditions, particularly diabetes and heart disease, which independently affect survival. Dialysis keeps you alive and functional, but the best long-term outcomes are associated with kidney transplantation for those who are eligible. Many people remain on hemodialysis for years, even decades, while waiting for or deciding against a transplant, and consistent adherence to the treatment schedule and dietary guidelines makes a measurable difference in how well and how long the treatment works.