Chronic kidney disease (CKD)
Chronic kidney disease is a description, not a cause.
It says the kidneys are filtering less well than they should, and have been for a while — the way “a fever” is a finding. It says nothing about why, and nobody stops at fever.
Stop reading and get help now if any of these apply
- Passing much less urine than usual, or none.
- Sudden swelling in your face, or swelling with shortness of breath.
- Chest pain, or trouble breathing when lying flat.
- Confusion, drowsiness you cannot shake, or a seizure.
- Blood in your urine, or urine the colour of cola.
None of those? Then nothing below is an emergency, and you can read the rest calmly.
Also on the list in an earlier edition
- One box — concerning. Ring your doctor’s office and ask for the triage nurse today.
- Two boxes — ring the triage nurse now, not later today.
- Three boxes — go to urgent care.
- Four or five boxes — ring 911, and expect that to mean the emergency room.
Not sure how serious this is? Where to call, and when.
Start with a phone call. Your doctor’s office has a triage line and a nurse will talk it through with you. They are genuinely good at this, they do it all day, and it costs nothing. Most practices have a phone line where a nurse takes calls about whether something needs to be seen, and how soon. It is often not advertised — you ring the main number and ask to speak to the triage nurse. There is no charge and you do not need an appointment to use it.
If it feels more serious than that, go to urgent care. You will usually be seen faster than at a hospital, and the care is good.
If it feels life-threatening, call 911 or go to the emergency room. Do not wait until you are sure.
Which one is yours to decide, not ours. But our advice is to assume it is worse than it looks and take the more cautious road. And trust your body — if it is telling you something is wrong, it is probably right. The best possible outcome of a trip to the emergency room is walking out saying well, that was a waste of an evening — but I feel a lot better knowing it is nothing serious.
Before you call, have these ready. They are what the nurse will ask, and the call goes better when you are not working them out on the phone.
- How bad is it, one to ten? Pick a number even if it feels arbitrary. They are not testing you — it gives them somewhere to start.
- When exactly did it start? Within the hour, six hours, today, yesterday, this week, longer. The number matters less than which side of “today” it falls on.
- Which way is it going? Better, worse, or the same — and if worse, over hours or over days. This is often the question that decides things, and it is the one people least often have an answer to.
- If there is a fever, the actual number and the time you took it. “I feel hot” and “101.4 at three o’clock” are very different pieces of information.
- Anything that affects your immune system, said early. Chemotherapy, steroids, immunosuppressants, a transplant, or a condition that affects it. It changes how they read everything else, so it should not come out at the end.
- What you have already tried, and whether it helped. What did not work narrows things down as much as what did.
- Anything new alongside it — vomiting and not keeping fluids down, bleeding, trouble passing urine, confusion, breathlessness. Combinations are read differently from single symptoms.
- Your medicines, including the ones started or stopped recently.
You are not diagnosing yourself by having this ready. You are handing them the things they would otherwise spend the call extracting — and the decision stays entirely theirs.
Writing to the portal instead of calling? The same list works, in that order, in one message. Put the direction it is going and the immune-system line near the top — portal messages get read quickly, and those two change how the rest is read.
Go deeper
3 layers below. Open any one.The stage comes from an estimate of how fast the kidneys filter, from a blood test. It measures how much, never why. Good evidence The estimate is calculated from creatinine, a muscle waste product — so someone who has lost muscle makes less of it, and the estimate can read better than the kidneys actually are. A second test, cystatin C, does not depend on muscle. Where the two disagree, the difference is information.
Not carelessness — usually the opposite. Diabetes or high blood pressure is a common, sufficient explanation, and the reasoning stops there. Most of the time it is right; when it is wrong, it is wrong quietly, for years. The one pattern that should reopen it: heavy protein in the urine. High-blood-pressure damage rarely causes heavy protein loss; diabetic damage that heavy usually shows in the eyes too. Heavy protein without those is a mismatch — a reason to look further.
Two sit inside this circle and are connected: MGRS (a small clone makes a protein that damages the kidney) and C3 glomerulopathy (complement that should idle runs on and deposits in the filters). In adults, especially after fifty, the first can be the cause of the second — and that look is often not made.
Questions to bring
Copy these, or read them out. They fit in a short visit.
- What is causing this, and how sure are we?
- How much protein am I spilling, and does that fit the cause we are assuming?
- Was a cystatin C done alongside the creatinine — do they agree?
- If the cause is not certain, is a kidney biopsy on the table?
The short version
- Getting ahead of it
- Treat it as a finding to explain, not a stage to accept; get the cause and the trend, and control blood pressure and protein early.
- Your testing regime
- Creatinine AND cystatin C, urine protein-to-creatinine, and last year’s and the year before’s numbers for the trend — on a fixed schedule.
- What they don’t tell you
- The eGFR estimate reads too good when muscle is low, and “stage” is a ruler, not a reason.
- What it can spawn
- Heart disease, anaemia, bone and mineral problems, and progression to failure.
- What it’s confused with
- Its own cause — MGRS or C3G get missed when diabetes or high blood pressure is assumed to be enough.
General clinical literature; nothing here comes from any individual’s medical record, graded where the evidence is established rather than universal.
Also asked as: kidney numbers that look normal while you feel worse · “is my kidney function getting worse” · “what does eGFR mean on my blood test” · “my kidney numbers are normal but I feel worse” · “will I need dialysis” (chronic kidney disease)
The longer chapter
From the 11 September 2026 edition (Vermont Synergy Initiative site): “What does eGFR mean on my blood test”. Every section below is that edition’s own words; open any one.
The short answer, before anything else.
eGFR is an estimate, not a measurement. It is calculated from creatinine, which comes from muscle. So it is answering a question about your kidneys using a number that also depends on how much muscle you are carrying.
A steady creatinine is not the reassurance it looks like. If muscle is being lost at the same time as kidney function, the two move in opposite directions and the number can sit still while things change underneath it.
Results from different years may not be comparable. Laboratories change the equation they use. A series that crosses one of those changes is two records, not one line.
The one thing to do next: Worth asking: “Would Cystatin C tell us something different? It does not depend on lean body mass.” and “Could we look at these in date order rather than one at a time?”
Everything below explains each of those, in whatever order suits you.
One of the things people type into Google most is what is a normal eGFR for my age
.
The honest answer is: normal compared to whom? Your own number from last year tells you more than any table. This room is about reading the trend, not the threshold.
The frail eighty-year-old with the beautiful creatinine.
A result that looks steady may not be.
A steady Creatinine result here is not the reassurance it looks like. It has barely moved — but Lean Body Mass is down 2% over the same stretch, and muscle makes creatinine.
Worth asking: “Would Cystatin C tell us something different? It does not depend on Lean Body Mass.”
A steady CK result here is not the reassurance it looks like. It has barely moved — but Lean Body Mass is down 2% over the same stretch, and CK is a muscle enzyme.
Tell me more — what is actually happening
Muscle makes creatinine. The kidney clears it. Lose muscle and you make less of it. Lose kidney and you clear less of it. The number sits still while both are going wrong.
Tell me more — why this fools people, and where else it happens
The kidney estimate assumes your muscle is average for your age and sex. When it isn't, the estimate carries that error forward. The fix is a marker your muscles don't make. Cystatin C is the usual one. The same trap turns up wherever a marker's source is fading. Albumin drops when someone stops eating well, not only when the kidney leaks. CK drops as muscle disappears, not only when injury stops. Urea depends on how much protein went in.
And the general rule
Before you read any trend, ask what makes this substance and whether that thing is changing too. If it is, a flat line means nothing and you need a second marker with a different source.
Where this comes from
Baxmann AC et al. Influence of muscle mass and physical activity on serum and
urinary creatinine and serum cystatin C. Clin J Am Soc Nephrol. 2008.
Shlipak MG et al. Cystatin C versus creatinine in determining risk based on
kidney function. N Engl J Med. 2013.
Her liver numbers improved when she changed hospitals. Her liver didn't.
Some of your results may not be comparable with each other.
AST came back 200.0 from Tufts on 2024-11-18, and 370.0 from SVMC on 2024-11-22 — 85% apart, days apart.
6 more like this for AST
AST came back 24.0 from SVMC on 2023-06-24, and 21.0 from Tufts on 2023-06-26 — 12% apart, days apart.
AST came back 21.0 from Tufts on 2023-06-26, and 27.0 from SVMC on 2023-06-29 — 29% apart, days apart.
AST came back 25.0 from SVMC on 2023-07-03, and 19.0 from Tufts on 2023-07-05 — 24% apart, days apart.
AST came back 23.0 from Tufts on 2023-09-12, and 28.0 from SVMC on 2023-09-14 — 22% apart, days apart.
AST came back 31.0 from SVMC on 2024-04-18, and 24.0 from Tufts on 2024-04-22 — 23% apart, days apart.
AST came back 25.0 from UIMC on 2024-10-04, and 39.0 from SVMC on 2024-10-07 — 56% apart, days apart.
Albumin came back 3.9 from Tufts on 2024-04-22, and 4.49 from DHMC on 2024-04-22 — 15% apart, days apart.
3 more like this for Albumin
Albumin came back 3.9 from SVMC on 2024-11-22, and 3.4 from Tufts on 2024-11-25 — 13% apart, days apart.
Albumin came back 3.4 from Tufts on 2024-11-25, and 3.8 from SVMC on 2024-11-27 — 12% apart, days apart.
Albumin came back 3.9 from RRMC on 2026-03-26, and 4.4 from DHMC on 2026-03-27 — 13% apart, days apart.
CK came back 4650.0 from Tufts on 2024-11-18, and 6650.0 from SVMC on 2024-11-22 — 43% apart, days apart.
Creatinine came back 1.66 from Tufts on 2023-06-26, and 2.1 from SVMC on 2023-06-28 — 27% apart, days apart.
6 more like this for Creatinine
Creatinine came back 1.5 from SVMC on 2023-06-24, and 1.66 from Tufts on 2023-06-26 — 11% apart, days apart.
Creatinine came back 1.66 from Tufts on 2023-06-26, and 1.9 from SVMC on 2023-06-29 — 14% apart, days apart.
Creatinine came back 1.22 from UIMC on 2024-10-04, and 1.4 from SVMC on 2024-10-07 — 15% apart, days apart.
Creatinine came back 1.2 from SVMC on 2024-11-22, and 1.32 from Tufts on 2024-11-23 — 10% apart, days apart.
Creatinine came back 1.2 from SVMC on 2024-11-22, and 1.05 from Tufts on 2024-11-25 — 12% apart, days apart.
Creatinine came back 1.05 from Tufts on 2024-11-25, and 1.2 from SVMC on 2024-11-27 — 14% apart, days apart.
Worth asking: “Are these comparable, or should I treat them as separate records?”
Tell me more — what is actually happening
Two labs can run the same test on the same blood and get different answers. They use different machines, calibrated differently, with their own idea of normal. Nobody reconciles them, because no single lab ever sees the other one's numbers.
Tell me more — why this fools people, and where else it happens
Each lab is internally consistent, so each one looks trustworthy on its own. The error only appears when you line them up, and lining them up is something only the patient is in a position to do. Watch for two shapes. A step in the level exactly where care moved. And two results days apart from different labs that disagree by more than the body could possibly move in that time.
And the general rule
A series is only a series if the same ruler measured all of it. Where the ruler changes, treat the step as an artefact until something proves otherwise.
Where this comes from
Standardisation of body composition parameters between GE Lunar iDXA and
Hologic Horizon A and their clinical impact. 2024.
Direct observation: in one longitudinal record, AST averaged 38.7 at one
hospital and 19.8 at another over overlapping years, same patient.
Normal every year for nine years. Then stage four. Nothing was ever abnormal — it was just always a little worse than last time.
Every one of these was normal, and every one of them was moving.
Every one of your Albumin results from DHMC came back inside the normal range (3.50 - 5.10 g/dL) — 30 of them. Over that stretch the number went from 3.87 to 4.6.
Worth knowing: DHMC did not use one range across those results. It used 3.50 - 5.10 g/dL and then 3.2 - 5.2 g/dL. The same number can sit inside one and outside the other.
Which direction is the worrying one for this test has not been settled here, so this is movement, not bad news.
Worth asking: “Could we look at these in date order rather than one at a time?”
Tell me more — what is actually happening
A normal range is built from a crowd. It says whether you look like other people. It cannot say whether you are moving, or how fast, or which way. Someone whose usual number is at the low end can lose a third of their function and still land inside the range every single time.
Tell me more — why this fools people, and where else it happens
Almost every alert in medicine fires on a threshold. Cross the line, something happens. Stay inside it and nothing does. So a person sliding steadily downhill inside the range triggers nothing, year after year, and each visit ends with good news that was true and useless. The direction and the speed carry the information. The position carries almost none.
And the general rule
Ask of any result: compared with this person's own past, which way and how fast? A number is a dot. Two dots are a difference. Only many dots are a direction.
Where this comes from
KDIGO defines chronic kidney disease by abnormality persisting over three
months — the criterion is duration, not a single value.
Roughly nine in ten adults with chronic kidney disease do not know they have it.
When to worry
- is my kidney function getting worse
- when should I go to the ER for kidney
- does foamy urine mean kidney disease
- swollen ankles at night kidney
What you can do yourself
- how much salt with kidney disease
- what to eat to protect my kidneys
- how much water should I drink kidney
What your results mean
- what does eGFR mean on my blood test
- creatinine normal but eGFR low
- my kidney numbers are normal but I feel worse
The things that are awkward to ask
- how much does dialysis cost
- can I keep working with kidney disease
- will I need dialysis
Print this, or post it to your portal the night before. It is not a diagnosis and it does not ask anyone to accept anything.
What I noticed
my rings don't fit
What I would like to ask
- Would Cystatin C tell us something different?
- Could we look at my CK in date order?
- Are my AST results from different labs comparable?
- Are my Albumin results from different labs comparable?
- Are my CK results from different labs comparable?
- Are my Creatinine results from different labs comparable?
- Could we look at my Albumin in date order?
This may not belong to one person
Swelling can come from the kidney, the heart or the liver, and each one makes the others worse. Whoever sees it first is the right person to start asking.
Could matter to: kidney, heart, liver
Muscle loss makes kidney results look better than they are, and it changes how drugs should be dosed. It matters to more than one of my doctors.
Could matter to: kidney, cancer care, nutrition, physical therapy
This page does not diagnose anything and does not replace your doctor. It reads your own records back to you and suggests questions. Nothing you type here leaves your device.
From an earlier edition
From the first edition of the Book (8–11 September 2026): “I was told my kidneys are failing and nobody has said why”. Every section below is that edition’s own words; open any one.
Rather listen?
Takes about 8 minutes, read aloud. It is the same words as the page below, so nothing is missing if you would rather read. Download it to keep on your phone — it will play with no signal, in a waiting room or a car.
The short answer
Chronic kidney disease is a description, not a cause. It says the kidneys are
filtering less well than they should and have been for a while. It says nothing about
why.
→ where this is explained: What those three words actually say
A stage is a measurement, not an explanation. Stage 3 means a filtering
estimate in a certain range on two occasions. Two people at the same stage can have
nothing else in common.
→ where this is explained: A stage is a ruler, not a reason
In a large share of cases nobody ever looks for the cause — not from
carelessness, but because a plausible reason is already on the chart.
→ where this is explained: Why the cause often goes unlooked-for
Chapter One · The label most people are given
The honest answer is: normal compared to whom? Your own number from last year tells you more than any table. This chapter is about reading the trend, not the threshold.
A stage number, a follow-up in six months, and no name for the cause.
Chronic means it has been present for at least three months. Kidney disease means the kidneys are not filtering as well as expected for your age, or that something is leaking through them that should not be — usually protein.
That is the whole content of the phrase. It is a finding, in the way that “a fever” is a finding. Nobody stops at fever.
The stage comes from an estimate of how fast the kidneys are filtering, calculated from a blood test. It is a useful ruler. It measures how much, never why.
Grade B The estimate itself has a known weakness worth understanding: it is calculated from creatinine, a waste product of muscle. Someone who has lost muscle produces less of it, so the estimate can read better than the kidneys actually are. A second test, cystatin C, does not depend on muscle. Where the two disagree, the difference is information.
Not carelessness. Usually the opposite — a reason is already on the chart.
If you also have diabetes or high blood pressure, either is a common and sufficient explanation for failing kidneys, and the reasoning stops there. Most of the time that reasoning is right. When it is wrong, it is wrong quietly and for years, because nothing prompts anyone to reopen it.
There is one pattern that should reopen it: heavy protein in the urine. Damage from long-standing high blood pressure does not usually cause heavy protein loss, and diabetic kidney damage that heavy is normally accompanied by diabetic changes in the eyes. Heavy protein without those is a mismatch, and a mismatch is a reason to look further.
Two causes sit inside the circle, and they are connected.
MGRS — a small number of cells in the bone marrow make one abnormal protein. Too few to be called a cancer. The protein itself damages the kidney.
C3 glomerulopathy — part of the immune system that is meant to idle instead runs continuously, and deposits in the kidney’s filters.
They are connected because in adults, particularly after fifty, the first can be the cause of the second. A finding of C3G in an older adult is a reason to look for a monoclonal protein, and that look is often not made.
“What do you think is causing this, and how sure are we?”
“How much protein am I spilling, and is that amount consistent with the cause we are assuming?”
“Has a cystatin C been done alongside the creatinine? Do the two agree?”
“If the cause is not certain, what would it take to find out — and is a kidney biopsy on the table?”
A free app called Insight Kidney walks through the kidney from the whole organ down to a single filter, and shows what changes at each stage, from one to five. It is the clearest picture of this we have found, and some people take in a shape far faster than a paragraph.
It is made by Anima Res, a German medical animation studio, and it was paid for by Novartis, who sell drugs for some of these conditions. We have no connection to either one. We link it because the anatomy is good, and we name who paid so you can weigh that yourself.
It is a phone app, and it opens outside this book. App Store · Google Play · what it is
Next chapter: My blood has an odd protein and my kidneys are getting worse
Written from the general clinical literature. Nothing on this page comes from any individual’s medical record. Where a statement rests on evidence that is established rather than universal, it carries a grade.