The Big 3
Three numbers that dialysis patients hear about constantly but rarely have explained to them in plain language. Here is what they actually mean, why they matter, and what they feel like when something is off.
What blood pressure actually is
Blood pressure is the force your blood puts on the walls of your blood vessels as your heart pumps. Think of it like water pressure in a hose. Too much pressure and the hose strains. Too little and nothing gets where it needs to go.
For dialysis patients, blood pressure is complicated because your kidneys normally help regulate it and your kidneys are no longer doing that job the way they used to. So your body compensates — sometimes overcompensating — and fluid buildup between sessions makes everything harder on your heart.
Understanding the two numbers in your reading
When your nurse reads your blood pressure as something like 120 over 80, those two numbers are telling two different stories about what your heart is doing. Here is what each one actually means.
The systolic number measures the pressure in your arteries at the moment your heart squeezes and pushes blood out through your body.
Think of it like the moment you squeeze a water balloon — that peak pressure as the squeeze happens is what the systolic number captures. Your arteries stretch slightly to absorb that push every single heartbeat.
For dialysis patients, this number is often elevated because extra fluid in your body means your heart is pushing against more resistance. The more fluid you are carrying, the higher this number tends to run.
The diastolic number measures the pressure in your arteries during the brief rest between heartbeats — the moment when your heart relaxes and refills before the next squeeze.
Using the water balloon again — this is the baseline pressure that remains in the balloon even when you are not squeezing it. Your arteries never fully relax to zero. There is always some resting pressure.
For dialysis patients, a diastolic number that stays elevated means your arteries are not getting a true rest between beats. Over time this keeps the whole cardiovascular system under constant strain.
Blood pressure is generally considered too low — a condition called hypotension — when it falls below 90/60 mmHg. During dialysis, a drop this significant means your organs and brain are not receiving enough blood flow. This is why your care team responds quickly when BP drops: it is not just about a number on a screen. It is about making sure your heart, brain, and body are getting what they need to keep functioning safely through your session.
Too much fluid between sessions puts extra pressure on your heart and blood vessels. The more fluid you carry into treatment, the harder your heart has been working since your last session.
High BP vs Low BP during treatment
High blood pressure coming into treatment is common when you have gained significant fluid weight. Your heart has been working overtime. Low blood pressure during treatment — called hypotension — is one of the most common and potentially dangerous events that can happen during a dialysis session. Both require attention. Both are manageable when caught early.
Intradialytic hypotension is when your blood pressure drops significantly during treatment. It is not just feeling a little dizzy. It is a real medical event that requires your nurse to respond immediately. If you feel any of the warning signs below during your session, tell your nurse right away — do not wait to see if it passes.
Hypotension heat map — during treatment
These ranges give a general picture. Your care team sets your individual thresholds. A drop that is significant for you may differ from another patient.
What happens when your blood pressure crashes during treatment
When blood pressure drops suddenly during dialysis, your care team moves quickly. Here is what a hypotensive response typically looks like — so you are not surprised or frightened if it happens to you:
significantly
slowed or stopped
flat or legs raised
through machine
applied to stabilize
When blood pressure crashes, your nurse will often recline your chair completely flat and raise your legs. This is deliberate. Lying flat helps blood return to your heart and brain more easily when pressure is too low to circulate it properly upright. It is not a sign that something has gone terribly wrong — it is the standard, correct response. Stay as still and calm as you can and let your care team work.
If your blood pressure drops significantly, your nurse may place an oxygen mask or nasal cannula to help stabilize you. Low blood pressure means less oxygen is reaching your organs and brain. Supplemental oxygen supports your body while the team works to bring your pressure back up. This is a precautionary measure — not a sign of a heart attack or emergency requiring 911 in most cases. Your nurse will tell you if more serious intervention is needed.
Symptoms of hypotension — tell your nurse immediately if you feel these
These are real symptoms patients describe. You are not imagining them. Do not wait to mention them.
Many patients try to tough through early hypotension symptoms because they do not want to interrupt treatment or feel like they are causing trouble. Please do not do this. Catching a BP drop early allows your nurse to intervene gently — slow the machine, give a small saline bolus, recline your chair. Waiting until you nearly pass out means a more serious intervention. Your comfort and safety are not an inconvenience to your care team.
High BP symptoms — also worth reporting
Most patients say they notice a dull headache at the back of the head or neck before treatment. Some notice feeling more swollen in the face or ankles. Others notice feeling short of breath doing things that normally do not bother them — walking to the car, climbing a few steps.
These are signs your body is carrying more fluid than it can comfortably handle. They are worth mentioning to your care team even if they feel minor.
Consistently high blood pressure over months and years does real damage — to the heart, blood vessels, and remaining kidney function. It increases the risk of stroke, heart attack, and heart enlargement. Dialysis patients already carry higher cardiovascular risk. Keeping blood pressure managed is one of the most important things you can do.
This is not meant to frighten you. It is meant to give you a real reason to take your fluid gains seriously and to speak up when your numbers are consistently high.
Every kilogram of fluid you gain between sessions is approximately one liter of extra fluid your heart is pumping against. The machine removes it during treatment, but the higher your fluid gain, the faster the machine has to pull — and faster removal is what causes cramping, dizziness, and BP crashes during treatment.
This is why your care team talks about fluid limits. It is not about being controlling. It is about making your treatment more comfortable and protecting your heart.
Questions to ask your care team
- What is my target blood pressure before and after treatment?
- What is the blood pressure number that should trigger a response during my treatment?
- What should I do at home if my blood pressure reads above or below a certain number?
- Is my current fluid limit realistic for me and my lifestyle?
- Are any of my medications affecting my blood pressure during treatment?
- What is my average fluid gain between sessions and how does that compare to where I should be?
- Have I been having hypotensive episodes and what is causing them?
Nobody told me that the headaches I was getting every treatment day were related to my fluid gains. I thought I just had headaches. When I finally started tracking my weight every morning and staying closer to my fluid limit, the headaches almost completely stopped. The connection between what I drank and how I felt on treatment day was real — I just had to learn to see it.
What potassium does in your body
Potassium is a mineral your body uses to keep your heart beating in a steady rhythm and your muscles working properly. Healthy kidneys constantly regulate the amount of potassium in your blood. When kidneys are not working, potassium builds up between dialysis sessions — and there is no other way for your body to get rid of it until your next treatment.
Potassium problems can affect the electrical system of the heart. This is not something to wait on. High potassium is one of the more serious complications dialysis patients face and it can happen with no warning symptoms at all.
Symptoms you might feel
The difficult thing about high potassium is that many people feel nothing at all until it becomes serious. But these are the symptoms patients sometimes describe:
If you feel your heart beating irregularly or fluttering, or you feel sudden severe weakness, tell your nurse immediately if you are in treatment, or call your dialysis center or 911 if you are at home.
Hidden high-potassium foods
This is the part that catches a lot of people off guard. Many foods we think of as healthy are high in potassium. Here are the ones that surprise patients most:
| Food | Why It Surprises People | Level |
|---|---|---|
| Bananas | Classic "healthy" fruit — but very high in potassium | High |
| Potatoes (any kind) | Especially baked — even sweet potatoes | High |
| Tomatoes and tomato sauce | Hidden in pasta dishes and soups | High |
| Oranges and orange juice | Patients think it is just vitamin C | High |
| Avocado | Very popular — and very high potassium | Surprise |
| Salt substitutes | Often contain potassium chloride — not safer | Surprise |
| Nuts and seeds | Small portions, big potassium | Medium-High |
| Spinach and dark leafy greens | Healthy but concentrated potassium | High |
Dialysis is the only way to remove excess potassium from your blood. When you miss a treatment, potassium keeps building. A weekend already means 3 days between sessions for MWF patients. Missing a Monday treatment means 5 days of potassium accumulation from the Friday before.
This is one of the reasons missed treatments carry real risk that goes beyond just feeling worse — potassium can reach dangerous levels faster than patients expect.
Your potassium level is checked in your monthly bloodwork. You have the right to ask for your results. Your care team should explain what the number means and whether any dietary changes are recommended.
Ask specifically: "What was my potassium this month and is it where you want it to be?" That is a completely appropriate and normal question.
I ate avocados thinking I was eating healthy. I had no idea. My potassium kept coming back elevated and I could not figure out why. When someone finally showed me which foods were the problem, I was genuinely surprised. The foods they warn you about are not always what you would guess. Ask your dietitian to go through your actual diet with you — not a generic sheet — your actual diet.
Why phosphorus becomes a problem in kidney disease
Phosphorus is a mineral found in almost everything we eat. Healthy kidneys remove excess phosphorus constantly. When kidneys fail, phosphorus accumulates in the blood — and dialysis does not remove it as efficiently as it removes other waste. That means dietary choices and phosphorus binders matter a great deal.
High phosphorus often has no obvious symptoms for a long time. By the time patients notice problems, there has usually been months or years of accumulation working against their bones, blood vessels, and skin. This is why tracking it matters even when you feel okay.
What patients often notice
The itching that nobody warned you about
Ask dialysis patients what they least expected and many of them mention the itching. It is not like normal dry skin itching. It is deep, often without a visible rash, and tends to be worse at night or during and after treatment. High phosphorus is one of the main drivers. Calcium deposits in the skin tissue from long-term high phosphorus cause nerve irritation that can be relentless.
If you are experiencing significant itching, ask your care team specifically about your phosphorus levels. It is worth the conversation.
Hidden phosphorus in processed foods
Phosphorus from processed foods is absorbed more efficiently than phosphorus from natural sources — which means labels matter. Look for ingredients with "phos" in the name:
| Food / Ingredient | Why It Matters | Level |
|---|---|---|
| Processed cheese and fast food cheese | Phosphate additives — highly absorbed | High |
| Dark colas and sodas | Phosphoric acid listed as ingredient | High |
| Packaged meats (hot dogs, deli meat) | Phosphate preservatives | High |
| Instant oatmeal and flavored cereals | Phosphate additives often added | Surprise |
| Chocolate and chocolate drinks | Naturally high in phosphorus | Medium-High |
| Beer and dark ales | Often overlooked phosphorus source | Surprise |
Phosphorus binders are medications you take with meals. They bind to the phosphorus in food before it can be absorbed into your blood. This is why timing matters — taking them after eating is much less effective than taking them during your meal.
Many patients skip binders because they forget or feel like taking another pill. But binders are one of the most direct tools you have to control phosphorus. If your current binders are not working for you, there are several types — ask your care team if there is a better option for your routine.
When phosphorus stays high over time, it pulls calcium from bones to try to balance out the excess. This weakens bones and can cause fractures that happen more easily than expected. At the same time, the displaced calcium can deposit in blood vessels — a process called calcification — which stiffens the vessels and strains the heart.
This happens slowly and silently. You may not feel it happening. But your monthly labs tell the story. Asking about your phosphorus trend over several months is worth doing.
Many patients with itching never connect it to phosphorus. They buy lotions and creams that do not help, because the source is internal — not on the skin's surface. When phosphorus is brought under control through diet and binders, many patients say the itching improves significantly.
The connection between what you eat, whether you take your binders, and how your skin and body feel is real and direct. It just takes time to learn to see it.
Questions to ask your care team
- What is my current phosphorus level and where does my care team want it to be?
- Am I taking my binders correctly — with meals, not after?
- Is there a different binder option that might be easier for my routine?
- Is my itching related to my phosphorus levels?
- Can I speak with the renal dietitian specifically about phosphorus in my current diet?
The itching was unbearable for a long time. I tried everything I could find at the pharmacy. Nothing worked because the problem was not my skin — it was my phosphorus. When my levels finally came down, the itching got so much better. Nobody had explained the connection to me. I am telling you now because I wish someone had told me sooner.
Patient Advocate One is an educational platform only. This content does not provide medical advice, diagnosis, or treatment recommendations. Numbers and ranges shown are general references — your care team sets your individual targets. Always follow your care team's clinical guidance. If you are experiencing chest pain, severe shortness of breath, confusion, or a medical emergency, call 911 immediately.