Chronic Kidney Disease Stages Explained

Intro

Chronic kidney disease (CKD) is measured and classified using a staging system that combines two pieces of information: how well the kidneys filter blood (eGFR), and how much protein is leaking into the urine (albuminuria). Together, these give clinicians — and patients — a clearer picture of where someone stands and how closely they need to be monitored.

This guide explains the stages from 1 through 5, what they mean in practice, and what can be done to slow or prevent progression.

Key Points

CKD is staged using eGFR (kidney filtration rate) and urine albumin (protein leakage)
Stages run from 1 (mildest) to 5 (kidney failure); sub-stages 3a and 3b are important distinctions
Stage alone does not tell the whole story — albuminuria, rate of change, and underlying cause all matter
Most people with CKD, especially Stages 1–3, never reach kidney failure
Blood pressure control and blood glucose management are the most important tools for slowing progression
Dialysis and transplant are late-stage options, not inevitable outcomes

eGFR: The Filtration Rate

eGFR stands for estimated glomerular filtration rate. It estimates how much blood the kidneys filter per minute, adjusted for body surface area. It is derived from a blood test (serum creatinine), together with age and sex.

A quick reference:

eGFR (mL/min/1.73m²)	Meaning
90 or above	Normal or high
60–89	Mildly reduced
45–59	Mildly to moderately reduced
30–44	Moderately to severely reduced
15–29	Severely reduced
Below 15	Kidney failure

eGFR naturally declines slightly with age — roughly 1 mL/min/1.73m² per year after the age of 40. A modest decline in an older adult without other evidence of kidney damage is not automatically CKD. Context matters.

Albuminuria: Protein in the Urine

Albumin is a protein found in blood. Healthy kidneys keep albumin inside the bloodstream. When kidneys are damaged, albumin leaks into the urine — a sign of structural or functional impairment.

Albuminuria is measured using the urine albumin-to-creatinine ratio (ACR):

ACR	Category
Below 3 mg/mmol (< 30 mg/g)	A1 — Normal to mildly increased
3–30 mg/mmol (30–300 mg/g)	A2 — Moderately increased
Above 30 mg/mmol (> 300 mg/g)	A3 — Severely increased

High albuminuria (A2 or A3) carries an independent risk of CKD progression and cardiovascular disease — even in people with relatively preserved eGFR. It is not just a side note; it is a key part of the overall risk picture.

The Stages of CKD

Stage 1 — Kidney Damage with Normal Function

eGFR: 90 or above

At Stage 1, the kidneys are filtering blood normally or near-normally, but there is evidence of damage — most commonly albuminuria, abnormalities on imaging, or persistent blood in the urine. eGFR alone would not indicate CKD; it is the presence of damage markers that defines this stage.

Most people with Stage 1 CKD have no symptoms. Detection is usually incidental — found on routine testing for diabetes or blood pressure follow-up.

Outlook: With attention to underlying causes, function can remain stable. The focus is on preventing progression.

Stage 2 — Mild Reduction in Kidney Function

eGFR: 60–89

Stage 2 is characterised by mildly reduced filtration alongside evidence of kidney damage. Again, eGFR in this range without damage markers would not be classified as CKD — the combination matters.

Symptoms remain absent in most people. Regular monitoring, blood pressure control, and management of underlying conditions are the priorities.

Outlook: Many people with Stage 2 remain stable for years. Early intervention gives the best chance of preventing further decline.

Stage 3a — Mild to Moderate Reduction

eGFR: 45–59

Stage 3 represents the point where kidney impairment becomes more meaningful. The 3a sub-stage covers the less severe half of this range.

Mild complications may begin to appear — slightly elevated blood pressure or mild anaemia — though most people still have no noticeable symptoms.

Outlook: Regular monitoring is recommended. Some people remain at Stage 3a for many years.

Stage 3b — Moderate to Severe Reduction

eGFR: 30–44

Stage 3b carries meaningfully higher risk than 3a — both of progression to later stages and of cardiovascular disease. People in this stage are more likely to have complications such as anaemia, bone mineral problems, or difficulty maintaining blood pressure.

Referral to a nephrologist (kidney specialist) is often recommended at Stage 3b, particularly if eGFR is declining or albuminuria is high.

Outlook: More intensive monitoring and management. With optimal control of blood pressure and blood glucose, some people stabilise here.

Stage 4 — Severe Reduction in Kidney Function

eGFR: 15–29

Stage 4 is advanced CKD. Waste products and fluid begin to accumulate. Complications including anaemia, elevated phosphate, altered calcium metabolism, and cardiovascular risk become significant.

At this stage, planning for future kidney replacement therapy (dialysis or transplant) begins — not because it is imminent, but to allow time for preparation if needed.

Symptoms may start to appear: fatigue, reduced appetite, swelling.

Outlook: Close specialist management. Some people remain at Stage 4 for years with careful treatment.

Stage 5 — Kidney Failure (End-Stage Kidney Disease)

eGFR: below 15

At Stage 5, kidney function is insufficient to adequately filter waste and maintain fluid and electrolyte balance. This is end-stage kidney disease (ESKD).

Kidney replacement therapy — dialysis or kidney transplantation — becomes necessary when symptoms of kidney failure emerge. Not everyone with an eGFR below 15 begins dialysis immediately; clinical judgement, symptoms, and patient preference all factor in.

Kidney transplantation, where possible, generally provides better long-term outcomes than dialysis.

Why Stage Alone Does Not Tell the Whole Story

CKD staging is not purely about the eGFR number. Two people at Stage 3a may have very different outlooks depending on:

Rate of decline — an eGFR falling by 5 mL/min/year is far more concerning than a stable eGFR of 50 over five years
Albuminuria level — someone with Stage 3a and A3 albuminuria has a substantially higher risk of progression than someone with Stage 3a and A1
Underlying cause — treatable causes (hypertension, obstruction, medication-related) carry better prospects than progressive glomerular diseases
Cardiovascular health — for many people with CKD, cardiovascular disease is a greater near-term risk than kidney failure

CKD staging is a useful tool for communicating risk and guiding monitoring frequency — but prognosis is always individual.

What Progression Means

Progression in CKD is defined by:

A sustained decline in eGFR over time (typically >5 mL/min/1.73m² per year)
Worsening albuminuria category (e.g. from A1 to A2)
Movement from one CKD stage to a higher one

Not all CKD progresses. A significant proportion of people — particularly those with Stage 1–3 CKD detected early and managed well — remain stable for the rest of their lives without reaching kidney failure.

Slowing Progression: What Works

The most effective strategies for slowing CKD progression are well established:

Blood pressure control Maintaining blood pressure below 130/80 mmHg (and sometimes lower in people with significant albuminuria) is among the single most important interventions for kidney protection.

Blood glucose management In people with type 2 diabetes and CKD, tight blood glucose control reduces the rate of kidney damage. This is why diabetes management and kidney management are closely linked.

Medicines with kidney-protective effects

ACE inhibitors and ARBs — these blood pressure medicines also reduce albuminuria and have direct kidney-protective effects
SGLT2 inhibitors (such as empagliflozin and dapagliflozin) — originally diabetes drugs, now shown in large trials to slow CKD progression independently of blood glucose effects
GLP-1 receptor agonists — growing evidence suggests these may also reduce CKD progression, particularly in people with diabetes and obesity; see Could GLP-1 Drugs Help Protect the Kidneys?

Lifestyle factors

Stop smoking — smoking accelerates kidney disease progression and cardiovascular risk
Reduce salt intake — helps with blood pressure management
Maintain a healthy weight — obesity contributes to both diabetes and hypertension
Avoid NSAIDs (ibuprofen, naproxen) regularly — these reduce blood flow to the kidneys and can accelerate decline
Stay well hydrated, but do not over-drink

Regular follow-up Monitoring frequency depends on stage and albuminuria. People at higher risk should have eGFR and urine albumin checked regularly — often every 3–6 months for advanced stages.

Dialysis and Transplant

Dialysis and kidney transplantation are treatments for kidney failure — Stage 5 CKD — not for earlier stages.

Dialysis replaces some kidney function by filtering waste products and excess fluid from the blood. It does not restore kidney function or reverse CKD. There are two main forms: haemodialysis (typically done at a clinic several times per week) and peritoneal dialysis (done at home daily).

Kidney transplantation involves placing a donated kidney (from a living or deceased donor) into the body. A successful transplant generally provides better quality of life and survival than dialysis, though it requires lifelong immunosuppression and is not suitable for everyone.

The key message: these are options that become relevant only at the most advanced stage, and for many people with CKD, they are never needed.

FAQ

Q: What is a normal eGFR? A: An eGFR of 90 or above is considered normal for most adults. However, eGFR naturally declines with age — an eGFR of 60–75 in an older adult without other signs of kidney damage may not indicate disease. Context matters.

Q: Is Stage 3 CKD serious? A: Stage 3 is moderate CKD and warrants medical attention, but many people with Stage 3a or 3b CKD live with stable kidney function for many years. The priority is identifying and managing causes to prevent progression.

Q: What is the difference between Stage 3a and 3b? A: Both are Stage 3, but 3a (eGFR 45–59) represents milder impairment than 3b (eGFR 30–44). Stage 3b carries a higher risk of progression and cardiovascular disease, and typically requires closer follow-up.

Q: Can you reverse CKD stages? A: In most cases, CKD damage is not reversible. However, the goal of treatment is to stabilise kidney function — and some people with Stage 1 or 2 CKD caused by a treatable condition may see improvement. Progression is not inevitable.

Q: When does CKD become kidney failure? A: Kidney failure (Stage 5, or ESKD) is defined as an eGFR below 15 mL/min/1.73m². Dialysis or transplant becomes necessary when symptoms of kidney failure emerge — not automatically at a particular number.

Q: Does everyone with CKD need dialysis eventually? A: No. The majority of people with CKD — especially those diagnosed in early stages — never reach kidney failure. Even in Stage 4, careful management can sometimes maintain adequate kidney function for years.