Renal impairment stages describe the degree to which kidney function is reduced or kidney damage is present.

In chronic kidney disease (CKD), doctors do not classify a patient only by creatinine. Current KDIGO guidance recommends describing CKD according to three major components:

• Cause of kidney disease

• GFR category

• Albuminuria category

This approach is often called CGA classification.

The estimated glomerular filtration rate, or eGFR, is an important measurement because it provides an estimate of how effectively the kidneys are filtering blood.

However, an eGFR number should always be interpreted together with urine findings, medical history and whether the abnormality has persisted over time.

At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides individualized evaluation and management for patients with abnormal kidney function and different stages of renal impairment.

Understanding eGFR Before Looking at Kidney Stages

eGFR is estimated from blood-test information, commonly including serum creatinine.

It is reported in mL/min/1.73 m² and is used to categorize kidney function.

A lower eGFR generally indicates reduced filtration.

However, one abnormal eGFR does not necessarily establish chronic kidney disease. CKD involves abnormalities of kidney structure or function that persist for more than three months.

This distinction is important because a temporary reduction in kidney function may occur during:

• Dehydration

• Acute infection

• Low blood pressure

• Urinary obstruction

• Certain medication effects

• Acute kidney injury

• Other serious illnesses

The cause and duration of the abnormal result therefore matter.

Renal Impairment Stages Based on eGFR

The current GFR categories used in CKD classification are:

GFR category	eGFR range	General description
G1	≥90	Normal or high
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	<15	Kidney failure range

These categories are part of the KDIGO CKD classification system.

Importantly, G1 or G2 does not automatically mean that a person has CKD. When eGFR is 60 or higher, there generally needs to be another marker of kidney damage, such as persistent albuminuria or another structural or functional abnormality, for CKD to be diagnosed.

Stage 1 Renal Impairment: G1

G1 corresponds to an eGFR of 90 or higher.

This represents normal or high filtration.

However, a person is not considered to have CKD simply because the eGFR is 90 or above.

There must be another persistent indication of kidney damage, such as:

• Albumin in urine

• Certain urine abnormalities

• Structural kidney abnormalities

• Imaging abnormalities

• Specific inherited kidney disorders

• Other evidence of kidney damage

If kidney damage is identified early, appropriate monitoring and treatment may help reduce the risk of progression.

Stage 2 Renal Impairment: G2

G2 corresponds to an eGFR of 60–89 mL/min/1.73 m².

This represents mildly decreased GFR.

Again, an eGFR in this range alone does not establish CKD.

Persistent evidence of kidney damage is required when the eGFR remains above 60.

Doctors may investigate:

• Urine albumin

• Blood in urine

• Blood pressure

• Diabetes

• Kidney imaging

• Family history

• Previous kidney injury

Management focuses on identifying the cause and controlling factors that could contribute to further kidney damage.

Stage 3 Renal Impairment

Stage 3 is divided into two categories.

G3a

An eGFR of 45–59 is classified as G3a.

Kidney filtration is mildly to moderately reduced.

Some people may have few or no symptoms at this stage.

Doctors may monitor:

• Creatinine and eGFR

• Urine albumin

• Blood pressure

• Blood glucose

• Electrolytes

• Hemoglobin

• Other CKD complications when appropriate

G3b

An eGFR of 30–44 is classified as G3b.

Kidney function is moderately to severely reduced.

The risk of complications and progression is generally greater than in earlier GFR categories, although individual risk varies considerably.

Medication doses may also need review because some medicines are cleared through the kidneys.

Stage 4 Renal Impairment: G4

G4 corresponds to an eGFR of 15–29.

This represents severely decreased kidney function.

At this stage, closer nephrology follow-up is often important.

Possible complications may include:

• Anemia

• High blood pressure

• Fluid retention

• Potassium abnormalities

• Acid-base disturbances

• Bone and mineral abnormalities

• Nutritional problems

• Uremic symptoms as kidney failure advances

Stage 4 does not automatically mean that dialysis must begin.

Instead, the nephrologist monitors kidney function and complications while preparing for possible kidney replacement therapy if it eventually becomes necessary.

Stage 5 Renal Impairment: G5

G5 corresponds to an eGFR of less than 15 mL/min/1.73 m² and is classified as the kidney failure range.

At this level, kidney function is severely reduced.

Patients may develop complications related to accumulation of fluid, electrolytes and waste products.

Depending on the clinical situation, treatment planning may include:

• Hemodialysis

• Peritoneal dialysis

• Kidney transplantation

• Conservative kidney management in selected patients

An eGFR below 15 does not mean that dialysis is automatically started on the same day. Dialysis decisions depend on symptoms, complications, laboratory abnormalities, fluid status and the overall clinical condition.

Why Albuminuria Is Important in Renal Impairment

Looking only at eGFR can give an incomplete picture.

Albuminuria measures the amount of albumin being lost through the urine and provides additional information about kidney damage and risk.

KDIGO classifies albuminuria into three categories:

Albuminuria category	Urine ACR
A1	<30 mg/g
A2	30–299 mg/g
A3	≥300 mg/g

Higher persistent albuminuria is associated with greater kidney and cardiovascular risk.

Therefore, two people with the same eGFR may have different levels of risk if their urine albumin levels are different.

Why the Cause of Renal Impairment Matters

Renal impairment can develop from many different diseases.

Common causes include:

Diabetes

Long-term diabetes can damage the kidney's filtering structures.

High Blood Pressure

Persistent hypertension can damage blood vessels and kidney tissue.

Glomerular Diseases

Conditions affecting the glomeruli can cause proteinuria, hematuria and reduced filtration.

Polycystic Kidney Disease

Inherited cystic disorders can progressively affect kidney structure and function.

Recurrent Kidney Stones or Obstruction

Repeated obstruction may damage kidney tissue in certain circumstances.

Autoimmune Diseases

Conditions such as lupus nephritis and other immune-mediated diseases can affect kidney function.

Acute Kidney Injury

Severe acute illness can temporarily or permanently reduce kidney function.

Knowing the underlying cause helps the nephrologist select appropriate treatment and estimate the likelihood of progression.

What Symptoms Occur at Different Renal Impairment Stages?

Symptoms do not always correspond closely to the eGFR category.

Early CKD can be silent, with the abnormality discovered through blood or urine testing. NIDDK notes that testing may be the only way to identify kidney disease in many people.

As kidney function becomes more impaired, some people may develop:

• Tiredness

• Swelling of the feet or ankles

• Changes in urine

• Foamy urine

• Loss of appetite

• Nausea

• Muscle cramps

• Itching

• Sleep difficulties

• Breathlessness

• Difficulty concentrating

These symptoms are not specific to CKD and require appropriate evaluation.

How Is Renal Impairment Diagnosed?

A kidney evaluation usually involves more than one test.

Serum Creatinine and eGFR

Creatinine is measured through a blood test and used in an equation to estimate GFR.

Modern eGFR equations are designed to estimate filtration without a race coefficient.

Urine Albumin Testing

A urine albumin-to-creatinine ratio can identify albumin leakage.

Urinalysis

A urine examination can detect:

• Blood

• Protein

• Infection

• Other abnormalities

Blood Pressure

Blood pressure is particularly important because hypertension can both contribute to and result from kidney disease.

Imaging

Ultrasound or other imaging may be recommended to investigate:

• Kidney size

• Obstruction

• Stones

• Cysts

• Structural abnormalities

Additional Investigations

Depending on the suspected cause, a nephrologist may recommend:

• Blood counts

• Electrolytes

• Calcium and phosphorus

• Blood glucose or HbA1c

• Autoimmune tests

• Genetic testing

• Kidney biopsy

Not every patient requires all of these investigations.

Can Renal Impairment Improve?

Sometimes.

Whether kidney function can improve depends on the cause.

For example, kidney function may improve after treatment of certain cases of:

• Dehydration

• Acute infection

• Medication-related kidney injury

• Urinary obstruction

• Acute kidney injury

Established chronic kidney damage is different. Scarring that has developed over a long period may not be completely reversible.

The treatment goal may therefore be to stabilize kidney function and reduce further damage.

Does Renal Impairment Always Progress?

No.

CKD does not inevitably progress to kidney failure.

Some people remain stable for many years, while others experience gradual or more rapid deterioration.

Progression risk is influenced by:

• Underlying cause

• eGFR

• eGFR trend

• Albuminuria

• Blood pressure

• Diabetes

• Cardiovascular disease

• Smoking

• Recurrent acute kidney injury

• Medication factors

• Other medical conditions

This is why monitoring over time is more informative than relying on a single kidney-function result.

What Treatment Is Used at Different Renal Impairment Stages?

Treatment is based on the underlying disease and complications rather than the stage number alone.

Protecting Kidney Function

Depending on the diagnosis, management may include:

• Blood-pressure control

• Diabetes management

• Treatment of significant albuminuria

• Appropriate kidney-protective medicines

• Avoiding unnecessary kidney-harming medicines

• Managing cardiovascular risk

• Appropriate dietary advice

• Regular kidney-function monitoring

KDIGO's current CKD guidance emphasizes individualized risk assessment and management according to kidney function, albuminuria and the underlying condition.

Managing CKD Complications

As renal impairment becomes more advanced, doctors may need to address:

• Anemia

• Potassium abnormalities

• Acidosis

• Fluid retention

• Mineral and bone disorders

• Nutritional problems

Treatment should be individualized according to laboratory results and clinical status.

What Happens When Kidney Function Reaches the Kidney Failure Range?

When eGFR reaches the G5 range, the nephrologist assesses whether kidney replacement therapy is required.

Options can include:

Hemodialysis

Blood is filtered using a dialysis machine and dialyzer.

Peritoneal Dialysis

The peritoneal membrane inside the abdomen is used as part of the dialysis process.

Kidney Transplantation

For appropriately selected patients, transplantation can provide functioning kidney tissue and is an important treatment option for kidney failure.

Conservative Kidney Management

Some patients may choose or be considered for comprehensive non-dialysis management depending on age, overall health, symptoms, treatment goals and personal preferences.

How Can You Protect Kidney Function?

Regardless of renal impairment stage, several measures may help protect kidney health.

• Keep blood pressure under appropriate control.

• Manage diabetes if present.

• Take prescribed medicines correctly.

• Avoid unnecessary NSAID use.

• Do not use unverified kidney supplements or detox products.

• Follow an individualized kidney-friendly diet.

• Avoid smoking.

• Maintain appropriate physical activity.

• Attend scheduled blood and urine tests.

• Report significant changes in urine output or swelling.

• Keep follow-up appointments with your healthcare team.

Fluid intake should also be individualized. People with advanced CKD or dialysis may have fluid restrictions, so drinking excessive water is not automatically beneficial.

When Should You See a Nephrologist?

A nephrologist may be appropriate when there is:

• Persistent reduction in eGFR

• Significant albuminuria

• Increasing creatinine

• Unexplained blood in urine

• Rapid decline in kidney function

• Difficult-to-control hypertension

• Recurrent kidney stones or obstruction

• Electrolyte abnormalities

• Suspected glomerular disease

• Advanced CKD

Early specialist assessment can help identify the cause and establish an appropriate monitoring and treatment plan.

Kidney Care for Renal Impairment at Prabhakar Bhurke Clinic

At Prabhakar Bhurke Clinic, Dr. Sandip Prabhakar Bhurke, super specialist nephrologist and transplant physician, provides individualized care for patients with abnormal kidney function and different stages of renal impairment.

Depending on the patient's condition, evaluation and management may include:

• Interpretation of creatinine and eGFR

• Assessment of urine albumin and protein

• Identification of the underlying kidney disease

• Blood-pressure management

• Diabetes-related kidney care

• Electrolyte and acid-base assessment

• Evaluation of CKD complications

• Monitoring kidney-function trends

• Advanced CKD management

• Dialysis planning when appropriate

• Kidney transplant-related evaluation

The treatment plan is based on the patient's cause of kidney disease, kidney-function trend, laboratory findings and overall health.

Frequently Asked Questions

What are the main renal impairment stages?

The GFR categories are G1, G2, G3a, G3b, G4 and G5. They range from eGFR ≥90 in G1 to less than 15 in G5.

What eGFR is considered kidney failure?

An eGFR below 15 mL/min/1.73 m² is classified as G5 or the kidney failure range. However, dialysis is not determined by eGFR alone.

Is stage 3 kidney disease serious?

Stage 3 represents eGFR 30–59 and is divided into G3a and G3b. It warrants appropriate monitoring and management, but the outlook varies according to albuminuria, cause and other risk factors.

Is stage 4 renal impairment reversible?

Established chronic kidney damage is generally not completely reversible, but reversible contributors can sometimes be treated and further deterioration may be slowed.

Does stage 5 always mean dialysis?

No. G5 means eGFR below 15, but the decision to begin dialysis depends on the patient's symptoms, complications and overall clinical condition.

Can kidney function improve from one stage to another?

It can in some situations, particularly when an acute or reversible cause is responsible for a temporary decline. A persistent chronic decline is managed differently.

Why is urine protein important when assessing renal impairment?

Persistent albuminuria can indicate kidney damage and provides additional information about the risk of kidney disease progression and cardiovascular complications.

Can a person have kidney disease with a normal eGFR?

Yes. A person can have evidence of kidney damage, such as persistent albuminuria or structural abnormalities, even when eGFR is normal or high.

Conclusion

Understanding renal impairment stages requires more than looking at a creatinine value or assigning a stage from one blood test.

The current CKD framework considers the cause of kidney disease, GFR category and albuminuria. eGFR categories range from G1, representing normal or high filtration, through G5, which represents the kidney failure range.

Early renal impairment may produce few noticeable symptoms, making blood and urine testing particularly important for people at risk. As kidney function declines, treatment focuses on identifying the cause, controlling risk factors, managing complications and preserving remaining kidney function.

Advanced renal impairment may require preparation for dialysis, kidney transplantation or conservative kidney management, depending on the individual clinical situation.

For personalized evaluation of kidney function and renal impairment stages, consult Dr. Sandip Prabhakar Bhurke at Prabhakar Bhurke Clinic.

Medical Disclaimer

This article is intended for general educational and informational purposes only and should not be considered a substitute for professional medical diagnosis, treatment or individualized medical advice. Renal impairment stages are based primarily on GFR categories but must be interpreted with the underlying cause, albuminuria, duration of abnormality, symptoms and other clinical findings. A single creatinine or eGFR result does not necessarily establish chronic kidney disease. Do not start, stop or change prescription medicines, supplements, diet or fluid intake based solely on this article. Dialysis should not be started or avoided based only on an eGFR number. Consult Dr. Sandip Prabhakar Bhurke or another qualified nephrologist for appropriate evaluation and treatment.