Before you go
- Bring your medicines list. Not a memory of it. The actual list, with what you take and when.
- Bring something warm. Units are kept cool, and passing your blood through a machine cools it further. People are often surprised by how cold they feel. A blanket or a jumper is not a luxury.
- Bring something to do for four hours. Headphones, a tablet, a book, a podcast. This is dead time you cannot get back, and the people who cope best tend to be the ones who claim it for something.
- Wear the right clothes. Sleeves that roll up easily above the fistula, or a top that gives access to a chest catheter.
- Ask about your blood pressure tablets. Many units ask patients to hold certain ones on dialysis days, because they make a blood pressure crash more likely. This is an individual instruction from your team. Do not change your own medicines.
The session, step by step
You are weighed
Before every session, in similar clothing. The gap between today's weight and your dry weight (the weight at which you are carrying no excess fluid) determines how much fluid the machine will remove.
Being weighed is not a moral event. Nobody is judging you. The number is the prescription: it is how the machine is told what to do.
Observations
Blood pressure, sitting and often standing. Pulse. Temperature. Your access is looked at and felt.
You settle into the chair
A reclining chair, which you will be in for the whole session. You can sit up or lie back.
You are connected
If you have a fistula or graft: two needles go in, one to take blood out and one to return it. They are larger than blood-test needles. Most units offer local anaesthetic cream or an injection, and you should ask for it if you want it.
If you have a catheter: no needles at all. The caps come off under sterile conditions and the lines connect directly. Staff will wear a mask and gloves.
The honest bit: the first few needlings can hurt. Most people report it becomes much easier as the fistula toughens, as the skin adapts, and as the staff learn your access.
The machine starts
Blood is pumped slowly out through the tubing and the filter, and returned to you. Only a small volume, roughly a cupful, is outside your body at any moment. An anticoagulant, usually heparin, is given to stop the circuit clotting, unless there is a reason you should not have it.
During the session
The machine controls the blood flow, the flow of dialysis fluid and the rate at which fluid is removed. Your blood pressure is checked regularly, typically every 15 to 60 minutes depending on the unit and how stable you are. You can usually read, sleep, work, talk or watch something.
The alarms go off
They will, and it is not a crisis. Alarms are usually a kinked line, a change in your position, or a pressure limit being touched. Staff respond to them constantly, all day. Nobody is alarmed by the alarm.
Coming off
The blood in the circuit is returned to you. The needles come out and pressure is held on the sites, usually for ten minutes or more, until the bleeding stops. Then you are weighed again.
Bleeding that takes more than 30 minutes to stop should be reported (National Kidney Foundation).
Afterwards
You may feel fine. You may feel tired. You may feel completely wiped out. Many people describe a washed-out feeling for a few hours, and some for the rest of the day. It tends to improve over the first weeks, and it is generally worse when a large volume of fluid has been taken off.
Why the first session is deliberately gentle
Your first treatment will usually be shorter and slower than the ones that follow. It is important that you know this is on purpose, because otherwise it is easy to read as a sign that something is wrong.
The reason is a condition called dialysis disequilibrium syndrome. If waste (urea) is cleared from the blood faster than it can leave the brain, water follows the concentration difference into brain tissue and causes swelling. It produces headache, nausea, restlessness and confusion, and in severe cases seizures. The strongest risk factors are a first dialysis treatment, a very high urea level to begin with, being very young or very old, and pre-existing neurological disease.
So the first session is done carefully: typically a short treatment, a low blood flow rate, a smaller filter, and a target of removing only a fraction of the urea rather than as much as possible. Protocols vary between units. The message is the same everywhere.
The common side effects, and what the team does about them
The blood pressure drop
Clinicians call it intradialytic hypotension, and it is the commonest acute complication of haemodialysis. It feels like light-headedness, nausea, yawning, sweating, cramp, anxiety, tunnel vision, or simply "going flat". Sometimes it happens with no warning at all.
What the team does at the time: lays the chair flat and raises your legs, slows or stops the fluid removal, and if needed gives a small bolus of fluid (usually saline).
What actually prevents it is more interesting, and it is where you have real leverage: getting your dry weight right, limiting how fast fluid is pulled off, cooling the dialysis fluid, reviewing when you take your blood pressure tablets, not eating during the session if you are susceptible, and, above all, reducing how much fluid you gain between sessions. Less gained means less to remove, means gentler removal, means fewer crashes. And the single biggest lever on the fluid you gain is not willpower about drinking. It is salt.
Cramps
Usually in the legs and feet, usually late in the session, and usually when a lot of fluid is being taken off or you are being pulled below your true dry weight. The team may slow or stop the fluid removal, stretch or massage the muscle, give a small fluid bolus, or reassess your dry weight upwards. The long-term answer is the same as for the blood pressure drop: gain less fluid between sessions, so less has to come off in each one.
The washed-out feeling
Post-dialysis fatigue is very common, can last hours, and is badly under-treated. It tends to track how much fluid was removed and how fast. What helps: gentler fluid removal, correcting anaemia, cooling the dialysis fluid in some people, exercise (yes, really), and where it is possible, moving to more frequent or longer dialysis, or to peritoneal dialysis, neither of which delivers the same intermittent hit.
The other things nobody warns you about
Headache. Nausea. Chest or back discomfort. Itching. Restless legs. Feeling cold during the session. And, later, low mood, which is common and treatable and deserves the same attention as any physical symptom. All of them should be reported. None of them is a complaint you are too much trouble for making.
What good looks like, after a few weeks
The uraemic symptoms start lifting: appetite comes back, the nausea and the metallic taste fade, the fog clears, sleep improves. The needling stops being an event. You learn your own rhythm, which day you feel best, and how to plan around the sessions rather than under them.
It is genuinely hard at the start, and it does genuinely get easier. Both of those are true, and you are allowed to hold them at the same time.
Two things will help more than anything else in the first months: learning to look after your access and understanding salt, fluid and potassium, because between them they decide how gentle or how brutal each session is going to be.
When to seek urgent help
Some things cannot wait until your next session. If you recognise yourself here, act now.
Call your local emergency number now
Bleeding from your fistula, graft or catheter that will not stop with firm, continuous pressure
Blood loss from a dialysis access can be rapid and life-threatening. Press hard, do not let go, and call for help.
Chest pain or tightness, or pain spreading to the arm or jaw
This can be a heart attack. Heart disease is the leading cause of death in people on dialysis.
Severe breathlessness, especially lying flat, waking up gasping, or coughing pink frothy sputum
Fluid on the lungs. This can be fatal and may need urgent dialysis.
Collapse, fainting, a seizure, or new confusion
Could be a dangerous drop in blood pressure, a dangerous potassium level, a stroke, or dialysis disequilibrium.
Palpitations with dizziness, or a very slow or very irregular pulse, especially after a missed session
Suggests a high potassium level or an abnormal heart rhythm. Severe hyperkalaemia can stop the heart.
Sudden weakness or numbness of the face, arm or leg on one side, or sudden trouble speaking or seeing
This can be a stroke. People on dialysis are at high risk, and treatment is time-critical.
Contact your dialysis unit today
The thrill (the buzz you can feel over your fistula or graft) is weak or gone
The access may be clotting. This is time-critical and it may still be saved if it is treated within hours.
Fever, shaking chills, or suddenly feeling very unwell, especially if you have a catheter
This can be a bloodstream infection. Catheters carry the highest infection risk of any access.
Cloudy drained fluid, tummy pain, fever, nausea or vomiting on peritoneal dialysis
Treat this as peritonitis until proven otherwise. Do not wait, and bring the drained bag with you.
Redness, heat, swelling, tenderness, pus or discharge at any access or exit site
An access or exit-site infection needs to be seen, not watched.
A cold, painful, numb, weak or pale hand on your access side
Possible steal syndrome, where the access diverts blood from the hand. A strong thrill does not rule it out.
You have missed a session, or you are about to miss one
Missing dialysis is dangerous, not merely inconvenient, and missing the session after the long weekend gap is the most dangerous of all. Call the unit. Never just skip.
New swelling of the ankles, face or abdomen, or new breathlessness on exertion, or a bigger weight gain than your unit agreed
Fluid is building up. It is far better to be reviewed early than to arrive with fluid on the lungs.
New or worsening low mood, hopelessness, or thoughts of harming yourself
Depression affects roughly a quarter of people on dialysis. It is treatable, and it is linked to missed treatments. Tell someone today.
Whatever else is happening
- Carry a card or wear an alert saying that you have kidney failure, that you are on dialysis, and which arm carries your access. No blood pressure cuff, no blood tests and no drips in that arm.
- Tell any doctor, dentist, pharmacist or paramedic that you are on dialysis before any treatment or prescription.
- Avoid anti-inflammatory painkillers such as ibuprofen, diclofenac and naproxen, and check every over-the-counter medicine and supplement with your kidney team or pharmacist.
- If in doubt, ring the unit. Dialysis units expect calls. They would far rather answer a question than admit you in an emergency.
This list is general information, not a diagnosis. It cannot cover everything, and it does not replace your kidney team. If something feels wrong and it is not on this list, ring the unit anyway.
Questions people ask
Will the needles hurt?
We are not going to tell you they do not. The needles used for dialysis are larger than the ones used for a blood test, and the first few sessions can genuinely hurt. Most units offer a local anaesthetic cream or an injection, and it is entirely reasonable to ask for it. What almost everyone reports is that it gets much easier: the skin toughens, the fistula matures, you stop bracing, and the staff learn the map of your particular access. If it is still bad after several weeks, that is worth saying out loud rather than enduring, because there are things that can be done.
Can I eat during dialysis?
It depends on your unit and on you. Some units allow it and some discourage it, and the reason is not fussiness: eating during a session diverts blood to the gut, which can help trigger a drop in blood pressure. If you are prone to crashing during treatment, your team may ask you not to eat. Ask what the rule is where you are, and why.
Should I take my blood pressure tablets before dialysis?
Ask your team, and do exactly what they tell you. Many units ask patients to hold certain blood pressure medicines on dialysis days, because they increase the chance of the blood pressure dropping during treatment. But this is an individual instruction that depends on your medicines and your blood pressure, it is not a general rule, and you must never change your own medicines on the strength of something you read on a website, including this one.
How long until I feel better?
Many people notice that the uraemic symptoms, the nausea, the poor appetite, the itching, the fog, begin to lift within the first few weeks. The post-dialysis tiredness usually improves over the same period as your body adapts and your team fine-tunes your dry weight. If you are still feeling wiped out after every session months later, that is not something to accept quietly. It usually means the prescription needs adjusting.
Sources
- Hemodialysis (NIDDK, US National Institutes of Health)
- Dialysis disequilibrium syndrome: prevention and management (International Journal of Nephrology and Renovascular Disease, 2019)
- Diagnosis and treatment of intradialytic hypotension in maintenance hemodialysis patients (Clinical Journal of the American Society of Nephrology, 2018)
- Hemodialysis access: caring for your access (National Kidney Foundation)