What Is Chronic Kidney Disease?

Intro

Chronic kidney disease (CKD) is not a single condition. It is an umbrella term for persistent, long-lasting kidney damage or a reduction in kidney function — usually defined as lasting three months or more.

CKD is one of the most common serious conditions in the world. It is also one of the least recognised by the people who have it. Most people with early to moderate CKD have no symptoms and no idea their kidneys are not working as they should.

Key Points

CKD means the kidneys are damaged or not filtering blood efficiently — persisting for three months or more
It is very common and often has no symptoms until it is advanced
The most common causes are type 2 diabetes and high blood pressure
Early detection relies on blood and urine tests, not symptoms
CKD can often be slowed but not reversed
Most people with CKD never reach kidney failure — but all stages carry increased cardiovascular risk

What the Kidneys Do

The kidneys are two bean-shaped organs that sit on either side of the spine, below the ribcage. Each is roughly the size of a fist.

Their main jobs include:

Filtering blood — removing waste products and excess fluid, which leave the body as urine
Regulating blood pressure — through control of fluid volume and hormone signals
Balancing electrolytes — sodium, potassium, phosphorus, and bicarbonate levels
Producing hormones — including erythropoietin (which stimulates red blood cell production)
Activating vitamin D — needed for bone health and immune function

Healthy kidneys filter around 180 litres of blood every day. When this process is impaired — even partially — the effects ripple across many body systems.

What CKD Means

CKD is defined as either:

Kidney damage shown by abnormal urine, blood, or imaging tests, or
Reduced kidney function — an eGFR below 60 mL/min/1.73m²

…persisting for three months or more.

The “chronic” in CKD distinguishes it from acute kidney injury (AKI), which develops rapidly over hours or days and may be reversible. CKD represents sustained loss of kidney capacity — gradual in most cases, with damage that usually cannot be fully undone.

Common Causes

CKD does not have a single cause. It develops from long-term damage from one or more sources.

Metabolic and vascular causes (most common):

Type 2 diabetes — the leading cause of CKD worldwide. Persistently high blood glucose damages the small blood vessels that supply the kidney’s filtering units (diabetic nephropathy)
High blood pressure (hypertension) — sustained high pressure damages the kidneys’ delicate filtration structures
Obesity — contributes through its effects on blood pressure, blood glucose, and additional metabolic pathways

Kidney-specific causes:

Glomerulonephritis — inflammation affecting the glomeruli (the kidney’s filtering units)
Polycystic kidney disease (PKD) — an inherited condition causing fluid-filled cysts in the kidneys

Other causes:

Autoimmune conditions — including lupus and IgA nephropathy
Recurrent kidney infections — repeated pyelonephritis can lead to scarring
Obstruction — kidney stones, enlarged prostate, or structural problems that block urine flow
Certain medicines — including long-term use of NSAIDs (ibuprofen, naproxen) and some antibiotics

In many people, no single cause is identified. Age, genetics, and cumulative damage all play a role.

Why CKD Is Often Silent

The kidneys have significant reserve capacity. In early stages, healthy tissue compensates for damaged areas — and the body gives no warning. Symptoms, when they do appear, tend to reflect advanced disease.

By the time symptoms such as fatigue, fluid retention, or reduced urination develop, CKD may already be at a late stage.

This is why screening matters — particularly for people with type 2 diabetes, high blood pressure, a family history of kidney disease, or established cardiovascular disease.

How CKD Is Measured

eGFR — Estimated Glomerular Filtration Rate

eGFR estimates how efficiently the kidneys filter blood. It is calculated from a blood test (serum creatinine), along with age and sex.

A rough guide to eGFR ranges:

90 or above — normal or high (if damage is also present, this may still be CKD Stage 1)
60–89 — mildly reduced
30–59 — moderately reduced
15–29 — severely reduced
Below 15 — kidney failure territory

A single low reading is not diagnostic. CKD requires the finding to persist over at least three months.

Urine Albumin / Protein

Albumin is a protein found in blood. Healthy kidneys keep albumin out of urine. When the kidneys are damaged, albumin leaks through — a condition called albuminuria or proteinuria.

Urine albumin is measured as the albumin-to-creatinine ratio (ACR):

Normal: below 3 mg/mmol (below 30 mg/g)
Mildly elevated (A2): 3–30 mg/mmol
Severely elevated (A3): above 30 mg/mmol

Both eGFR and urine albumin are used together to classify CKD severity and predict risk. See Chronic Kidney Disease Stages Explained for the full staging system.

When to Seek Medical Advice

Speak to a doctor if:

You have type 2 diabetes and have not had a recent kidney function test
You have high blood pressure that is difficult to control
You have a family history of kidney disease or polycystic kidney disease
A routine blood or urine test has flagged a concern about kidney function
You are taking regular NSAIDs or other medicines that may affect the kidneys

If you have risk factors for CKD, regular monitoring is usually recommended even if you feel well.

Red Flags — Seek Urgent Care

Seek urgent medical attention if you experience:

Sudden, marked change in urine output — much less or much more than normal
Severe swelling of the legs, ankles, or around the eyes
Difficulty breathing (which may indicate fluid build-up)
Confusion, severe fatigue, or difficulty concentrating
Dark, foamy, or blood-coloured urine

These may indicate rapidly worsening kidney function requiring prompt assessment.

FAQ

Q: Can CKD be cured? A: CKD is generally not reversible, but it can often be slowed significantly with the right treatment and lifestyle changes. For some people — especially those with early-stage CKD and treatable causes — function can stabilise for many years.

Q: Does CKD always progress to kidney failure? A: No. Most people with CKD — especially those diagnosed at early stages — never reach kidney failure. The goal of management is to slow progression and reduce cardiovascular risk. Many people live with stable, mild CKD for decades.

Q: Will I know if my kidneys are failing? A: Not necessarily, especially in early stages. CKD is usually silent until it is advanced. This is why blood and urine tests are important for people with risk factors, even when they feel well.

Q: Is CKD the same as kidney failure? A: No. CKD covers a spectrum from mild to severe kidney impairment. Kidney failure (end-stage kidney disease, or ESKD) is the most severe end of the spectrum, where the kidneys can no longer function adequately without dialysis or a transplant.

Q: Can I develop CKD without diabetes or high blood pressure? A: Yes, though these are the two most common causes. Autoimmune conditions, inherited diseases, repeated infections, and other factors can all cause kidney damage. Some people develop CKD with no identifiable cause.

Q: Can children get CKD? A: Yes, though it is far less common in children. When it does occur, inherited or congenital causes — such as abnormal kidney development or polycystic kidney disease — are more likely than in adults.