ENKIKnowledge libraryCKD basics
CKD stages explained
CKD is classified using both estimated filtration, called the G category, and urine albumin, called the A category. A stage is useful shorthand, but it does not describe the whole person or predict an exact outcome.
This guide helps you understand terms and prepare questions. It cannot diagnose a condition or tell you to change treatment. Seek local medical care for urgent or severe symptoms.
Start here
Three points to keep
- G1 and G2 require another persistent marker of kidney damage to count as CKD.
- A lower eGFR and a higher urine ACR generally mean higher risk.
- Trend, cause, age, other conditions, and treatment response also matter.
The eGFR categories
The G category is based on eGFR in mL/min/1.73 m². Boundaries help standardize care, but a result close to a boundary should not be overinterpreted.
| Category | eGFR | General description |
|---|---|---|
| G1 | 90 or higher | Normal or high filtration |
| G2 | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | Below 15 | Kidney failure |
The albuminuria categories
Urine albumin-to-creatinine ratio, or ACR, adds important information that eGFR cannot provide. Units vary by country, so compare the result with the unit printed by the laboratory.
| Category | ACR mg/g | ACR mg/mmol | General description |
|---|---|---|---|
| A1 | Below 30 | Below 3 | Normal to mildly increased |
| A2 | 30–300 | 3–30 | Moderately increased |
| A3 | Above 300 | Above 30 | Severely increased |
Why both categories matter
A person may have a relatively preserved eGFR but substantial albuminuria, or reduced eGFR with little albuminuria. These patterns can carry different risks and may point toward different causes.
Clinicians combine G and A categories with the cause of CKD to estimate the chance of progression, cardiovascular events, and complications. One result is not a countdown to dialysis.
Stage changes and trends
Small movements can occur because of hydration, illness, medicines, laboratory variation, or normal biological variation. A sudden fall may represent an acute kidney injury and should not simply be relabeled as a new chronic stage.
The most useful view is a sequence of comparable results over time, interpreted alongside urine albumin and clinical events.
For your next visit
Questions worth taking with you
- 01What are my current G and A categories?
- 02Is the change large enough to be clinically meaningful, or should it be repeated?
- 03What does my combined risk category mean for follow-up?
Evidence trail
Sources
ENKI prioritizes current clinical guidelines and public-health sources. Links open on the publisher's website.
Published by the ENKI Health Editorial Team under our editorial policy.