Chronic Kidney Disease (CKD)

Chronic kidney disease (CKD) is a lasting reduction in kidney function — defined as kidney damage or an eGFR below 60 mL/min/1.73m² for at least three months. It is staged by eGFR, not by a single creatinine number.

Clinicians describe CKD with two measures together: a GFR category (G1–G5) and an albuminuria category (A1–A3). Combining them gives the KDIGO risk picture.

Explore CKD

• CKD stages by eGFR (G1–G5) — the full staging table, start here
• Stage 3 kidney disease — eGFR 30–59 — the most common stage
• KDIGO risk heat map — eGFR × albuminuria risk grid
• When dialysis is started — why it is based on eGFR and symptoms
• eGFR calculator — estimate your filtration rate

How CKD Is Defined

CKD has a precise definition: kidney damage or an eGFR below 60 mL/min/1.73m², present for at least three months. The three-month requirement separates lasting disease from a temporary dip caused by dehydration, illness, or a new medicine. Kidney damage can be shown by albuminuria, abnormal imaging, or other markers even when eGFR is still normal — which is why the earliest stages, G1 and G2, are only called CKD when there is other evidence of damage. From stage G3 onward, the reduced eGFR alone meets the definition.

How CKD Is Staged

Staging uses two measures together. The first is the GFR category, running from G1 (normal or high) through G2 (mildly decreased), G3a and G3b (the most common stages), G4 (severely decreased), and G5 (kidney failure). The second is the albuminuria category: A1 (under 30 mg/g), A2 (30–300 mg/g), and A3 (over 300 mg/g). Pairing them — for example “G3a A2” — gives a fuller picture than either measure alone, because albuminuria adds risk at any filtration level. The combined view is the KDIGO risk heat map, which grades progression risk from low to very high.

Common Causes of CKD

Chronic kidney disease usually develops slowly over years, and the two leading causes are diabetes and high blood pressure. Other causes include glomerular diseases, polycystic kidney disease, repeated urinary or kidney infections, and long-term use of certain medicines. Because the early stages often cause no symptoms, CKD is frequently picked up on routine blood and urine tests rather than because a person feels unwell. Managing the underlying cause — keeping blood sugar and blood pressure well controlled — is central to slowing any decline in kidney function.

Many people with early CKD never develop symptoms and keep stable kidney function for the rest of their lives. When symptoms do appear, usually at lower filtration levels, they can include tiredness, swelling, and changes in urination. Because these signs are non-specific, the diagnosis still rests on the eGFR and urine tests rather than on how a person feels.

How CKD Is Monitored Over Time

CKD is a long-term condition, so monitoring is about direction rather than a single result. A clinician usually tracks eGFR and albuminuria over months to years, alongside blood pressure and any underlying cause such as diabetes. A stable eGFR is reassuring even when it sits in a lower stage; a value that is sliding prompts a closer look and may lead to a change in management. The aim is to slow any decline and to manage related risks early, while most early-stage CKD stays stable for years.

Why eGFR, Not Creatinine Alone

A single creatinine value varies with muscle mass, age, and sex, so the same number can mean different things in different people. Estimated GFR adjusts for these factors, which is why CKD is staged by eGFR. Diagnosis also requires the change to be sustained, not a one-off reading. The same logic explains why even kidney failure and the timing of dialysis are judged by eGFR and symptoms, not by a fixed creatinine number. Most people with early CKD have stable kidney function for years, and the goal of monitoring is to spot a falling trend early so it can be managed with a clinician.