CKD diagnosis usually involves blood and urine tests that evaluate how well the kidneys filter waste and whether there are signs of kidney damage. The two most important measurements are estimated glomerular filtration rate (eGFR) and urine albumin, usually measured with a urine albumin-to-creatinine ratio (UACR).

Chronic kidney disease can develop gradually and often causes few or no noticeable symptoms in its early stages. This is why testing is particularly important for people with risk factors such as diabetes, high blood pressure, cardiovascular disease, or a family history of kidney failure.

A single abnormal kidney test does not always establish CKD. Healthcare professionals generally need evidence that reduced kidney function or kidney damage has persisted for at least three months, while also evaluating the possible cause.

What Is Chronic Kidney Disease?

Chronic kidney disease is a condition in which the kidneys have abnormalities in structure or function that persist over time.

Healthy kidneys filter waste and excess fluid from the blood and perform several other important functions, including helping regulate blood pressure, maintaining electrolyte balance, and supporting red blood cell production.

CKD can have many causes. Diabetes and high blood pressure are major causes in adults, but inherited kidney disorders, autoimmune diseases, infections, urinary tract problems, certain medications, and other conditions can also contribute.

Because early CKD may not cause obvious symptoms, laboratory testing plays an important role in finding it.

How Is CKD Diagnosed?

The two main tests

The core of a CKD diagnosis involves two measurements:

1. eGFR — estimates how well the kidneys filter blood.
2. Urine albumin, usually UACR — looks for albumin leaking into the urine, which can indicate kidney damage.

Healthcare professionals may repeat abnormal results to determine whether the finding is persistent rather than temporary.

Test	What it measures	Why it matters
Serum creatinine	Waste product in the blood	Used to estimate kidney filtration
eGFR	Estimated kidney filtration ability	Helps identify and classify reduced kidney function
UACR	Albumin compared with creatinine in urine	Detects and monitors kidney damage
Urinalysis	Blood, protein, cells, and other urine findings	Can provide clues about kidney damage or its cause
Blood tests	Electrolytes, BUN, glucose, and other markers	Help evaluate kidney function and complications
Imaging	Kidney structure and urinary tract	Can help identify structural causes
Kidney biopsy	Kidney tissue under a microscope	Used in selected cases to determine the cause

Understanding the Kidney Function Test

A kidney function test can refer to several laboratory tests, but serum creatinine and eGFR are especially important in CKD evaluation.

Serum creatinine

Creatinine is a waste product produced by normal muscle metabolism. Healthy kidneys remove creatinine from the blood.

When kidney filtration decreases, blood creatinine may rise. However, creatinine alone does not provide a complete picture of kidney function because levels can also be influenced by factors such as muscle mass, age, and other individual characteristics.

For this reason, healthcare professionals generally use serum creatinine as part of an equation to estimate GFR.

What is eGFR?

Estimated glomerular filtration rate (eGFR) is an estimate of how well the kidneys are filtering blood.

It is calculated using a validated equation, generally based on serum creatinine and relevant patient characteristics. Current approaches use equations that do not include a race coefficient.

An eGFR can help healthcare professionals identify reduced kidney function and determine the appropriate CKD category when interpreted together with other findings.

In general:

• An eGFR of 60 or higher may be within the expected range, depending on the overall clinical picture.
• An eGFR below 60 mL/min/1.73 m² may indicate reduced kidney function.
• A persistently reduced eGFR below 60 for at least three months is consistent with CKD when other explanations have been considered.
• An eGFR around 15 or lower is associated with kidney failure and requires careful medical evaluation.

These numbers should not be interpreted in isolation. Age, trends over time, urine albumin, other laboratory findings, and the clinical context all matter.

Why Urine Albumin Matters in CKD Diagnosis

A healthy kidney normally keeps most albumin in the bloodstream. When the kidney’s filtering structures become damaged, albumin can leak into the urine.

This condition is called albuminuria.

Urine albumin can sometimes provide evidence of kidney damage even when the eGFR is not substantially reduced.

Urine albumin-to-creatinine ratio

The urine albumin-to-creatinine ratio (UACR) is commonly used to assess albumin in urine.

A spot urine sample can be used for the test, making it more convenient than collecting urine over an entire day in routine situations.

A UACR:

• 30 mg/g or less is generally considered within the normal range.
• More than 30 mg/g may indicate abnormal albumin excretion and can be a marker of kidney damage.

An abnormal result may need to be repeated because temporary factors can affect urine albumin measurements.

Healthcare professionals may consider factors such as infection, strenuous exercise, blood pressure, blood glucose, and other clinical circumstances when interpreting an abnormal result.

Does One Abnormal Test Mean You Have CKD?

Not necessarily.

The word “chronic” is important. CKD refers to abnormalities that persist over time rather than a temporary change in kidney function.

For example, dehydration, acute illness, certain medications, or another temporary medical problem may cause a short-term change in creatinine or urine findings.

If an initial test is abnormal, a healthcare professional may repeat testing and review previous laboratory results to determine whether the abnormality has persisted.

Evidence of kidney damage or reduced kidney function for more than three months is an important part of establishing CKD.

This is one reason that looking at laboratory trends can be more informative than focusing on a single test result.

Other Tests Used During CKD Evaluation

Although eGFR and UACR are central to CKD assessment, healthcare professionals may order additional tests depending on the patient’s history and initial results.

Urinalysis

A routine urinalysis can identify findings such as:

• Blood in the urine
• Protein
• White blood cells
• Other abnormalities

These findings may provide clues about kidney damage or its possible cause.

Blood tests

Additional blood tests may include:

• Blood urea nitrogen (BUN)
• Electrolytes
• Glucose
• Calcium
• Phosphorus
• Albumin
• Complete blood count

These tests can help evaluate kidney-related complications and identify conditions that may contribute to kidney disease.

Imaging tests

Imaging may be appropriate when healthcare professionals need to evaluate kidney structure or look for possible obstruction or other abnormalities.

Depending on the clinical situation, imaging can include ultrasound, CT, MRI, or other appropriate studies.

Kidney biopsy

A kidney biopsy is not required for everyone with CKD.

In selected patients, a healthcare professional may recommend a biopsy to examine kidney tissue and determine the underlying cause. This can be particularly useful when laboratory and imaging findings do not adequately explain the kidney problem or when a specific kidney disease is suspected.

How Doctors Determine the Cause of CKD

Diagnosing CKD is only part of the evaluation. Healthcare professionals also try to determine why the kidneys are abnormal.

The evaluation may consider:

• Diabetes
• High blood pressure
• Cardiovascular disease
• Family history
• Autoimmune conditions
• Inherited kidney disorders
• Previous kidney injury
• Recurrent urinary problems
• Medication exposure
• Abnormal urine findings
• Imaging results
• Relevant infections or systemic diseases

Importantly, having diabetes does not automatically prove that diabetes is the cause of kidney disease. Other causes may need to be considered when the clinical findings do not fit typical diabetic kidney disease.

Who Should Be Tested for CKD?

Routine testing is particularly important for people at increased risk.

NIDDK identifies groups such as people with:

• Diabetes
• High blood pressure
• Cardiovascular disease
• A family history of kidney failure

as people who may benefit from kidney disease testing.

People with risk factors should discuss appropriate testing intervals with their healthcare professional. Testing recommendations can vary according to the person’s health history and clinical circumstances.

How CKD Is Classified After Diagnosis

Once CKD has been established, healthcare professionals generally classify it using both GFR category and albuminuria category.

The eGFR categories include:

GFR Category	eGFR (mL/min/1.73 m²)	General description
G1	≥90	Normal or high
G2	60–89	Mildly decreased
G3a	45–59	Mild to moderately decreased
G3b	30–44	Moderately to severely decreased
G4	15–29	Severely decreased
G5	<15	Kidney failure

Albuminuria is also categorized:

Category	UACR	General description
A1	<30 mg/g	Normal to mildly increased
A2	30–300 mg/g	Moderately increased
A3	>300 mg/g	Severely increased

These categories are not intended to be used by patients to self-diagnose CKD. Healthcare professionals interpret them alongside medical history, trends, symptoms, medications, and the suspected cause of kidney disease.

When Should You Talk With a Healthcare Professional?

People should discuss kidney testing with a healthcare professional if they have risk factors for CKD or receive abnormal blood or urine test results.

Medical evaluation is especially important when laboratory results show a persistent reduction in eGFR, elevated urine albumin, blood in the urine, or other unexplained kidney abnormalities.

Sudden changes in kidney function can represent acute kidney injury rather than CKD and may require prompt medical assessment.

Anyone with concerning symptoms or a significant change in health should seek appropriate medical care rather than relying on an online article or interpreting laboratory results independently.

Frequently Asked Questions About CKD Diagnosis

1. What is the main test for diagnosing CKD?

There is not just one test. The two key markers are eGFR and urine albumin, usually measured using a urine albumin-to-creatinine ratio. Healthcare professionals may use additional blood, urine, imaging, or biopsy tests depending on the situation.

2. Can CKD be diagnosed with a blood test?

Blood testing can provide important evidence of reduced kidney function. Serum creatinine is used to calculate eGFR. However, CKD evaluation also commonly includes urine testing because albuminuria can indicate kidney damage even when filtration is not severely reduced.

3. What does an eGFR below 60 mean?

An eGFR below 60 may indicate reduced kidney function, but one result does not necessarily establish CKD. Persistent reduction for at least three months is an important part of determining whether chronic kidney disease is present.

4. What does urine albumin indicate?

Albumin in urine can indicate damage to the kidney’s filtering structures. A UACR above 30 mg/g is considered abnormal and may be a marker of kidney disease. Abnormal results may need confirmation with repeat testing.

5. Can you have CKD with a normal eGFR?

Yes. Kidney damage, such as persistent albuminuria, can be present even when eGFR is 60 or higher. This is why both kidney filtration and urine albumin are considered when evaluating CKD.

6. Does CKD always cause symptoms?

No. Early CKD often causes few or no noticeable symptoms. Blood and urine testing may detect kidney abnormalities before a person feels unwell.

7. What happens after CKD is diagnosed?

Healthcare professionals generally evaluate the cause, classify the CKD using eGFR and albuminuria, assess cardiovascular and kidney-related risks, monitor kidney function over time, and develop an appropriate management plan based on the individual’s condition.

Conclusion

A CKD diagnosis usually requires more than a single abnormal laboratory result. Healthcare professionals look for evidence of persistent kidney damage or reduced kidney function, with eGFR and urine albumin serving as the two central markers.

A kidney function test can help estimate how effectively the kidneys filter blood, while UACR can identify albumin leakage that may signal kidney damage. Additional urine tests, blood work, imaging, or kidney biopsy may be appropriate when healthcare professionals need to investigate the cause or clarify the diagnosis.

Because early CKD may have few symptoms, people with risk factors such as diabetes, high blood pressure, cardiovascular disease, or a family history of kidney failure should discuss appropriate kidney testing with a qualified healthcare professional. Early identification gives the care team an opportunity to monitor kidney health and address factors that may contribute to progression.