The kidneys are among the few organs that can lose the majority of their working capacity while the person they belong to feels entirely well.
Two fist-sized organs filter the entire blood volume many times a day, removing waste, balancing salts and water, regulating blood pressure, activating vitamin D and signalling the bone marrow to make red blood cells. They have substantial reserve capacity, and they use it to hide their own decline.
By the time symptoms are unmistakable, kidney function is often severely reduced and much of the loss is permanent.
What chronic kidney disease is
CKD means kidney damage or reduced filtering function persisting for more than three months. It is graded in five stages based on estimated glomerular filtration rate — eGFR — which is calculated from a blood creatinine level along with age and sex.
- Stage 1–2: eGFR near normal, but with evidence of damage such as protein in the urine
- Stage 3: moderately reduced function, where most diagnoses are actually made
- Stage 4: severely reduced function, planning for replacement therapy begins
- Stage 5: kidney failure, requiring dialysis or transplantation
The important feature of this scale is how much of it is silent. Many people at stage 3 feel completely normal.
Who is at risk
The two dominant causes worldwide are the same two conditions responsible for most cardiovascular disease.
Diabetes. High blood glucose damages the small filtering vessels over years. Diabetic kidney disease is the single largest cause of kidney failure globally.
High blood pressure. Both a cause and a consequence. Damaged kidneys raise blood pressure, and raised blood pressure damages kidneys further — a loop that accelerates unless interrupted.
Other significant risk factors include cardiovascular disease, obesity, a family history of kidney disease, being over 60, recurrent kidney stones or urinary infections, autoimmune conditions such as lupus, long-term use of certain painkillers, smoking, and — in several tropical agricultural regions — repeated heat stress and dehydration among outdoor workers, which appears to drive an otherwise unexplained form of the disease.
The symptoms, and why waiting for them fails
Early CKD typically produces nothing at all. When symptoms do appear, they are vague enough to be attributed to almost anything.
- Tiredness that does not resolve with rest, partly from anaemia as the kidneys stop signalling for red blood cell production
- Swelling of ankles, feet, hands or around the eyes
- Frothy or bubbly urine, a sign of protein leaking through
- Needing to urinate more often at night
- Poor appetite, nausea, a metallic taste
- Itchy skin
- Muscle cramps, particularly at night
- Difficulty concentrating
- Blood pressure that is becoming harder to control
Every one of these has a dozen more common explanations. That is exactly the problem: the disease is not detected by noticing symptoms. It is detected by testing.
The two tests that find it
Both are inexpensive, widely available, and routinely skipped.
Blood creatinine, reported as eGFR. Creatinine is a waste product from muscle. When filtering falls, it accumulates. The result is converted into an estimated filtration rate.
Urine albumin-to-creatinine ratio. A urine sample checked for albumin, a protein that healthy kidneys retain. Protein in the urine is often the earliest detectable sign — it can appear years before eGFR moves, and it is also an independent predictor of cardiovascular risk.
Testing eGFR alone misses a significant proportion of early disease. Both together give a far more accurate picture, and current guidance in most countries recommends annual testing for anyone with diabetes, hypertension, cardiovascular disease, or a family history.
If you have any of those conditions and have never had a urine albumin test, that is worth asking about at your next appointment.
What can be done
CKD is generally not reversible, but progression can be slowed dramatically — often enough to keep a person from ever reaching dialysis.
Blood pressure control is the highest-value intervention. Targets are individualised, but tight control markedly slows decline.
Blood glucose control in diabetes, similarly.
Specific medication classes. Certain blood pressure drugs that act on the renin-angiotensin system reduce protein leakage and protect kidneys beyond their blood pressure effect. More recently, SGLT2 inhibitors — originally diabetes drugs — have been shown in large trials to slow CKD progression substantially, including in people without diabetes, and are now a standard part of treatment in many guidelines. This is one of the most significant changes in kidney medicine in decades and is worth discussing with a doctor if you have CKD.
Reduce salt. Lower sodium intake helps blood pressure and reduces protein leakage.
Be careful with painkillers. Regular long-term use of non-steroidal anti-inflammatory drugs such as ibuprofen and diclofenac can damage kidneys, particularly at reduced function or during dehydration. Occasional use for a headache is generally fine; daily use for chronic pain warrants a conversation.
Stop smoking. It accelerates decline measurably.
Avoid unregulated supplements and herbal remedies. Some contain compounds directly toxic to kidneys, and products bought without regulatory oversight have caused outbreaks of kidney failure in several countries.
Stay hydrated sensibly — enough that urine is pale, without forcing extreme volumes.
Protein and potassium may need adjusting at later stages, but this should be guided by a clinician or renal dietitian rather than self-imposed. Restricting nutrients unnecessarily causes its own harm.
The heart connection
People with CKD are considerably more likely to die of cardiovascular disease than to reach kidney failure. The two systems share risk factors and damage each other.
This means a CKD diagnosis is not only a kidney matter. It reclassifies someone as high cardiovascular risk, and managing cholesterol, blood pressure and diabetes becomes correspondingly more important.
When kidneys fail
At stage 5, options are haemodialysis, peritoneal dialysis, transplantation, or conservative management focused on symptom control and quality of life.
Transplantation generally offers the best outcomes and quality of life for those who are suitable candidates, though organ availability is the limiting factor almost everywhere. Planning early — including discussion of living donation where possible — produces better results than reaching the point of crisis first.
The short version
Kidneys fail quietly, and the symptoms arrive too late to be a useful alarm. If you have diabetes, high blood pressure, heart disease or a family history, ask for an eGFR blood test and a urine albumin test annually — both, not just the blood test. Controlling blood pressure and glucose, avoiding routine anti-inflammatory painkillers and unregulated supplements, and discussing newer protective medications with a doctor can slow the decline enough to change the outcome entirely.
This article is general information and not a substitute for medical advice. Anyone with risk factors or symptoms should speak with a clinician.
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