I Know What Too Much Salt Feels Like. High Potassium Feels Like Nothing.

It's eleven at night and my legs are itching. Not a mosquito-bite itch — something underneath the skin, in a place scratching can't reach. I scratch anyway. Then I lie there doing the arithmetic on what I ate, and by the time I stop doing arithmetic it's one in the morning.

If you're on dialysis, you know this night. You probably had one recently.

After years of this, I've learned to read my own body fairly well. Too much salt has a feeling. Phosphorus has a feeling. I can usually tell, hours later, that I got something wrong.

And that's exactly what makes the third one dangerous. Because potassium — the one that can actually stop your heart — doesn't feel like anything at all.

Salt: the fastest feedback

Sodium is the one I notice soonest, and it announces itself in three ways.

Thirst comes first, and it isn't ordinary thirst. It's the kind where water doesn't fix it. You drink, and twenty minutes later you want more. On a fluid restriction that's not an inconvenience — it's a whole evening of negotiating with yourself.

Then the weight. Salt makes you hold water, and held water shows up on the scale before the next session. That number isn't fat, it's fluid, and it has to come off during treatment.

Then the pressure. Not a headache exactly — a full, pushing feeling, like something is expanding behind my face.

And then the part that decides how the rest of your week goes: the timing.

If I dialyze on Friday and eat something salty on Saturday, there is no session between me and Monday. Two days of negotiating with my own thirst, hour by hour. Not a lapse — a stretch of heroic endurance over something as ordinary as a plate of food.

That gap is where salt does its real damage. Not because Saturday's meal was worse than Tuesday's, but because nothing is coming to take it off.

The useful thing about sodium is the speed of the signal. Eat a restaurant meal at eight, and by midnight you have your answer. Whether the lesson arrives on a Tuesday or on a Friday, though, is the difference between an inconvenience and a weekend.

Phosphorus: the slow one that steals your sleep

Itching is the one I hear about most from other patients, and the one clinicians underestimate the most.

It has a name — CKD-associated pruritus, sometimes called uremic itch. It's common: depending on the study, somewhere between a third and most people on dialysis deal with it at some point. It typically comes with no rash, nothing to show anyone. Just skin that won't settle down, often worse at night, often worse on the back, arms, legs.

And it costs more than comfort. Poor sleep, exhaustion the next day, shortened or skipped sessions — the itch has a way of unravelling a whole week.

Here's the part I want to be careful about, because it gets said wrong constantly, including by professionals: itching is not a phosphorus meter. High phosphorus is associated with it. So is parathyroid hormone, so is the calcium-phosphorus picture, so is inadequate dialysis, so is plain dry skin, so are things that aren't fully understood.

I've read an account from a patient whose phosphorus was inside her target range and who was still told the itching was her fault, that she wasn't watching her diet. She kept asking questions until her team found a real answer. That story stayed with me, because the "you must be cheating" reflex is common and it stops people from getting help.

So: if you're itching, tell your team. Don't assume it's your dinner, and don't accept being told it's your dinner without a blood test to back it up.

Potassium: nothing

Now the one that matters most.

Potassium is the mineral that keeps your heart's electrical rhythm steady. Too much of it disrupts that rhythm. At the severe end, that means arrhythmia and cardiac arrest.

And you will very likely feel nothing.

This isn't my theory. The American Heart Association puts it plainly: hyperkalemia is hard to diagnose because it often has no symptoms. Most people who have it find out from a routine blood test. When symptoms do appear, they're vague — weakness, fatigue, an odd heartbeat — the kind of thing you'd blame on a bad night's sleep, or on dialysis, or on getting older.

Worse: the symptoms don't track the severity. Someone can be at a genuinely dangerous level and feel fine, while someone else feels rough at a milder number, depending on how fast it rose.

There's a question I've seen a nephrology practice answer on their own website, and it's the exact question every one of us asks: If I feel fine, is high potassium still dangerous? The answer is yes.

That's the whole problem in one line. Salt gives you a headache. Phosphorus keeps you awake. Potassium says nothing and then, occasionally, says everything at once.

Why I stopped trusting how I feel

For a while I thought I was getting good at this. Read the body, adjust the food, repeat.

Then I understood what I was actually doing: I'd built a system that gives me feedback on the two things that will make me uncomfortable, and no feedback at all on the thing that could kill me. My body is a smoke alarm that works fine for burnt toast and stays silent for carbon monoxide.

Feeling fine is not information. It's the absence of information, which is a different thing entirely.

So now I do the boring version. I know roughly what's in what I eat, before I eat it — not to be perfect about it, but so I'm not reconstructing my day from memory at eleven at night.

That's why I built renalee. It doesn't decide what your limits are — your dietitian does that, based on your labs, your stage and your treatment. You put the targets they gave you into the app, and it estimates where a meal lands against those numbers. It gives no medical advice, and it isn't trying to. The guidelines those targets come from are listed on the medical sources page.

What it's for is discipline. Holding a balance between what I actually want to eat and what will let me feel decent five years from now — because a diet you resent is a diet you abandon.

I'll say the uncomfortable part out loud: the numbers it gives me are estimates. Portion sizes vary, the same dish is made differently in two kitchens, and food databases are averages. If you want exact, you need a blood draw, and nothing on your phone changes that.

I don't track to be precise. I track to know where the edges are — so that when the labs come back, they're a confirmation of something I already roughly knew, instead of a surprise.

The itching still tells me something. The thirst still tells me something. I just don't let them vote on potassium anymore.

What I'd tell someone starting out

Learn your body's signals — they're real, and they're useful for salt and fluid, where the feedback is fast enough to learn from.

Don't extend that trust to potassium. It hasn't earned it.

If you get sudden weakness, palpitations, chest pain, fainting — that's not a diet question, that's an emergency room question. Go.

And if you're lying awake scratching at one in the morning: tell your team at the next visit. It's a symptom, not a character flaw.