GFR Calculator

Kidney Function Calculator

GFR Calculator

Estimate kidney function using age, sex, and serum creatinine with the 2021 CKD-EPI creatinine equation without race.

eGFR Estimate eGFR estimates how well the kidneys filter blood, reported as mL/min/1.73 mยฒ.
Creatinine-Based This calculator uses serum creatinine, age, and sex to estimate kidney filtration.
CKD Staging Guide CKD staging also depends on persistence for 3 months and urine albumin or other kidney damage markers.

Calculate Estimated GFR

Enter your age, sex, and serum creatinine to estimate kidney function.

Adults only. Enter age in years.
Enter creatinine in mg/dL.
Estimated GFR —

eGFR is reported in mL/min/1.73 mยฒ and should be interpreted with clinical context.

GFR Category — Based on eGFR range
Kidney Function — General interpretation
Creatinine Used — Converted to mg/dL if needed
CKD Criteria — CKD requires persistent abnormality
Next Step — General guidance only
Equation CKD-EPI 2021 Creatinine, race-free
Important medical note: This calculator is for educational use only and does not diagnose kidney disease. CKD diagnosis usually requires abnormal kidney function or markers of kidney damage for at least 3 months. Urine albumin-to-creatinine ratio, repeat blood tests, medical history, medications, hydration status, pregnancy, muscle mass, and acute illness can affect interpretation.
Seek urgent medical care if you have very low urine output, severe swelling, shortness of breath, chest pain, confusion, severe weakness, very high potassium, suspected acute kidney injury, or rapidly worsening kidney results.

GFR Calculator: Understand Your Kidney Function and eGFR Result

Your kidneys filter waste, extra fluid, and toxins from your blood. A GFR Calculator, also called an eGFR calculator, helps estimate how well your kidneys are filtering blood based on your age, sex, and serum creatinine level.

This calculator uses the 2021 CKD-EPI creatinine equation without race, which is now recommended by the National Kidney Foundation and the American Society of Nephrology for estimating GFR.

This tool is for education only. It does not diagnose kidney disease, but it can help you understand your result and know when medical follow-up may be needed.

โœ… What Is GFR?

GFR stands for Glomerular Filtration Rate.

It estimates how much blood your kidneys filter each minute. A higher GFR generally means better kidney filtering function, while a lower GFR may suggest reduced kidney function.

GFR is usually reported as:

mL/min/1.73 mยฒ

This means milliliters per minute adjusted to a standard body surface area.

๐Ÿงช What Is eGFR?

eGFR means estimated Glomerular Filtration Rate.

Because measuring true GFR directly is complicated, most routine kidney function reports use an estimated value. eGFR is calculated from a blood test called serum creatinine, together with age and sex.

The NIDDK explains that doctors commonly use a blood test for GFR and a urine test for albumin to diagnose and monitor kidney disease.

๐Ÿงฌ What Is Creatinine?

Creatinine is a waste product produced by normal muscle activity. Your kidneys remove creatinine from your blood.

When kidney filtering function decreases, creatinine can rise in the blood. However, creatinine alone does not tell the full story because it can be affected by:

๐Ÿ’ช Muscle mass
๐Ÿฅฉ Diet
๐Ÿ’ง Hydration
๐Ÿ‹๏ธ Recent intense exercise
๐Ÿ’Š Certain medications
๐Ÿ‘ต Age
๐Ÿงฌ Body size
๐Ÿค’ Acute illness

This is why eGFR is often more useful than creatinine alone.

๐Ÿงฎ How This GFR Calculator Works

This calculator uses:

โœ… Age
โœ… Sex
โœ… Serum creatinine
โœ… Creatinine unit: mg/dL or ยตmol/L

It then estimates eGFR using the 2021 CKD-EPI creatinine equation.

The equation uses serum creatinine, age, and sex, and the 2021 version does not use race. The National Kidney Foundation lists the CKD-EPI 2021 creatinine equation as: eGFR = 142 ร— min(Scr/K, 1)^ฮฑ ร— max(Scr/K, 1)^-1.200 ร— 0.9938^Age ร— 1.012 if female.

๐Ÿ“Š eGFR Categories and Kidney Function Stages

eGFR results are often grouped into G categories.

๐ŸŸข G1: eGFR 90 or higher

This is considered normal or high kidney filtration.

Important: G1 does not mean chronic kidney disease by itself unless there are other signs of kidney damage, such as albumin in the urine.

๐ŸŸก G2: eGFR 60โ€“89

This is mildly decreased kidney filtration.

G2 also does not confirm chronic kidney disease by itself unless there are other markers of kidney damage, such as albuminuria, abnormal urine findings, or structural kidney problems.

๐ŸŸ  G3a: eGFR 45โ€“59

This suggests mild to moderately decreased kidney function.

If this persists for 3 months or more, it may be consistent with chronic kidney disease, especially if other kidney damage markers are present.

๐ŸŸ  G3b: eGFR 30โ€“44

This suggests moderate to severely decreased kidney function.

Medical follow-up is important, especially to check blood pressure, diabetes control, urine albumin, medications, and progression risk.

๐Ÿ”ด G4: eGFR 15โ€“29

This suggests severely decreased kidney function.

Prompt medical review is recommended. A kidney specialist may be needed depending on the cause, symptoms, rate of decline, and other test results.

๐Ÿšจ G5: eGFR below 15

This is often called kidney failure range.

This requires urgent specialist review, especially if the result is new, worsening, or associated with symptoms such as swelling, shortness of breath, confusion, very low urine output, or abnormal potassium levels.

โš ๏ธ Does a Low eGFR Always Mean Chronic Kidney Disease?

Not always.

Chronic kidney disease, or CKD, usually means kidney damage or reduced kidney function that lasts 3 months or more. The National Kidney Foundation explains that an eGFR below 60 for 3 months or more, or an eGFR above 60 with kidney damage such as high urine albumin, can mean CKD.

A single low eGFR may be caused by temporary or reversible issues such as:

๐Ÿ’ง Dehydration
๐Ÿค’ Acute illness
๐Ÿ’Š Medication effects
๐Ÿฆ  Infection
๐Ÿฉธ Low blood pressure or poor circulation
๐Ÿงช Lab variation
๐Ÿง Recent intense exercise
๐Ÿฅฉ High meat intake before the test

That is why repeat testing and clinical interpretation are important.

๐Ÿงซ Why Urine Albumin Matters

eGFR is only one part of kidney assessment. Another key test is urine albumin-to-creatinine ratio, often called uACR or ACR.

Albumin is a protein that should mostly stay in the blood. When kidney filters are damaged, albumin can leak into the urine.

The National Kidney Foundation explains that albumin in the urine can be a sign of kidney disease even when eGFR is above 60 or โ€œnormal.โ€

This means someone can have:

โœ… Normal eGFR but abnormal urine albumin
โœ… Low eGFR but normal urine albumin
โœ… Both low eGFR and high urine albumin

Both eGFR and urine albumin help estimate kidney risk.

๐Ÿฉบ Common Causes of Reduced Kidney Function

Many conditions can affect kidney function. Common causes include:

๐Ÿฉธ High blood pressure
๐Ÿฉบ Diabetes
โค๏ธ Heart disease
๐Ÿงฌ Family history of kidney disease
๐Ÿง‚ Long-term high salt intake
๐Ÿ’Š Long-term use of certain painkillers or nephrotoxic medicines
๐Ÿฆ  Recurrent kidney infections
๐Ÿงฑ Kidney stones or urinary blockage
๐ŸŒธ Autoimmune diseases
๐Ÿงฌ Polycystic kidney disease

The CDC explains that chronic kidney disease happens when kidneys are damaged and cannot filter blood as well as healthy kidneys, allowing waste and extra fluid to build up in the body.

๐Ÿšจ Symptoms of Kidney Problems

Early kidney disease may cause no symptoms, which is why blood and urine tests are important for people at risk.

Possible symptoms of kidney problems include:

๐Ÿ’ง Swelling in feet, ankles, legs, or around the eyes
๐ŸŒ™ Urinating more often at night
๐Ÿšฝ Very low urine output
๐Ÿ˜ด Fatigue or weakness
๐Ÿคข Nausea or poor appetite
๐Ÿง  Confusion or trouble concentrating
๐Ÿ˜ฎโ€๐Ÿ’จ Shortness of breath
๐Ÿฉธ Foamy urine or blood in urine
๐Ÿ“ˆ High blood pressure
๐Ÿ’ช Muscle cramps
๐Ÿงด Itchy skin

These symptoms can have many causes, but they should not be ignored.

๐Ÿ†˜ When to Seek Urgent Medical Care

Seek urgent medical help if you have:

๐Ÿšจ Very low or no urine output
๐Ÿšจ Severe swelling
๐Ÿšจ Shortness of breath
๐Ÿšจ Chest pain
๐Ÿšจ Confusion
๐Ÿšจ Severe weakness
๐Ÿšจ Fainting
๐Ÿšจ Blood in urine with pain or fever
๐Ÿšจ Very high potassium reported on blood test
๐Ÿšจ Sudden major increase in creatinine
๐Ÿšจ Suspected acute kidney injury

A very low eGFR or rapidly worsening kidney result should be reviewed promptly.

๐Ÿงพ Who Should Check eGFR?

You may need kidney function testing if you have risk factors such as:

โœ… Diabetes
โœ… High blood pressure
โœ… Heart disease
โœ… Family history of kidney disease
โœ… Older age
โœ… History of kidney stones
โœ… Recurrent urinary infections
โœ… Autoimmune disease
โœ… Long-term use of medicines that may affect kidneys
โœ… Previous abnormal kidney blood or urine tests

NIDDK notes that diabetes and hypertension are leading causes of CKD in adults, and key markers used to identify kidney disease include abnormal urine albumin and persistent reduction in eGFR.

๐Ÿ’Š Medicines and eGFR

eGFR can affect medication dosing. Some medicines need dose adjustment when kidney function is reduced.

Examples may include certain:

๐Ÿ’Š Antibiotics
๐Ÿ’Š Diabetes medicines
๐Ÿ’Š Blood pressure medicines
๐Ÿ’Š Pain medicines
๐Ÿ’Š Anticoagulants
๐Ÿ’Š Antiviral medicines
๐Ÿ’Š Heart medicines

Do not stop prescribed medication without medical advice. If your eGFR is low, ask your doctor or pharmacist whether any medicines need adjustment.

๐Ÿฅ— How to Support Kidney Health

Healthy habits can help protect kidney function, especially if you have risk factors.

โœ… 1. Control Blood Pressure

High blood pressure can damage kidney blood vessels over time. Follow your healthcare providerโ€™s blood pressure plan, take medicines as prescribed, and monitor regularly if advised.

โœ… 2. Manage Blood Sugar

For people with diabetes or prediabetes, blood sugar control is important for kidney protection.

โœ… 3. Check Urine Albumin

Ask your healthcare provider about urine albumin-to-creatinine ratio, especially if you have diabetes, high blood pressure, or reduced eGFR.

โœ… 4. Stay Hydrated

Dehydration can affect kidney blood flow and creatinine concentration. Hydration needs vary depending on health conditions, climate, activity, and heart or kidney status.

โœ… 5. Be Careful With Painkillers

Frequent or high-dose use of some painkillers, especially NSAIDs such as ibuprofen or naproxen, may affect kidney function in some people. Ask your healthcare provider if they are safe for you.

โœ… 6. Reduce Excess Salt

High salt intake can worsen blood pressure and fluid retention. Reducing sodium can support blood pressure and kidney health.

โœ… 7. Avoid Smoking

Smoking can worsen blood vessel health and increase kidney and heart risks.

โœ… 8. Maintain a Healthy Weight

Excess weight increases the risk of diabetes, high blood pressure, and kidney disease.

๐Ÿง  Why eGFR Can Change Over Time

eGFR may fluctuate slightly between tests. Small changes do not always mean kidney disease is worsening.

Possible reasons include:

๐Ÿ’ง Hydration status
๐Ÿฅฉ Recent high-protein meal
๐Ÿ‹๏ธ Heavy exercise before testing
๐Ÿ’Š Medication changes
๐Ÿค’ Illness or infection
๐Ÿงช Lab variation
๐Ÿ“‰ Blood pressure changes
๐Ÿฉธ Acute kidney injury

Doctors usually look at trends over time, not just one result.

๐Ÿ“Œ Practical Example

Imagine someone enters:

๐Ÿ”น Age: 45
๐Ÿ”น Sex: Male
๐Ÿ”น Serum creatinine: 1.0 mg/dL

The calculator estimates eGFR and places the result into a G category.

If the result is above 90, kidney filtration may be normal.
If the result is below 60, repeat testing and urine albumin testing may be needed to see whether the reduction is persistent.
If the result is very low or worsening quickly, medical review is important.

โ“ Frequently Asked Questions

What is a normal GFR?

An eGFR of 90 or higher is often considered normal or high, but interpretation depends on age, urine albumin, medical history, and other kidney damage markers.

Is eGFR the same as kidney function?

eGFR is an estimate of kidney filtering function. It is one of the most important kidney function measures, but it should be interpreted with urine albumin, symptoms, medical history, and repeat testing.

What eGFR means kidney disease?

An eGFR below 60 for 3 months or more may indicate chronic kidney disease. An eGFR above 60 can still be associated with kidney disease if there are other signs of kidney damage, such as albumin in the urine.

Can eGFR improve?

Sometimes, yes. If reduced eGFR is due to dehydration, acute illness, medication effects, or temporary kidney stress, it may improve. Chronic kidney disease may not fully reverse, but progression can often be slowed with proper care.

Why is my creatinine high?

Creatinine may rise due to reduced kidney filtration, dehydration, high muscle mass, intense exercise, certain medicines, high meat intake, or acute illness. A healthcare professional should interpret it with eGFR and other tests.

What is the difference between creatinine and eGFR?

Creatinine is a waste product measured in the blood. eGFR is a calculated estimate of kidney filtering function based on creatinine, age, and sex.

What is urine ACR?

Urine ACR stands for albumin-to-creatinine ratio. It checks whether albumin is leaking into the urine, which can be a sign of kidney damage.

Can I have kidney disease with normal eGFR?

Yes. Albumin in the urine can be a sign of kidney disease even if eGFR is above 60.

Should I use this calculator for children?

No. This calculator is intended for adults. Children require pediatric kidney function equations and clinical interpretation.

Should I use this calculator during pregnancy?

Pregnancy changes kidney physiology, so eGFR equations may not be reliable in the same way. Pregnant people should follow clinician guidance.

โœ… Final Thoughts

The GFR Calculator is a useful educational tool for understanding kidney filtering function. It estimates eGFR using age, sex, and serum creatinine with the 2021 CKD-EPI creatinine equation without race.

However, eGFR is only one part of kidney health. A complete kidney assessment often includes repeat blood tests, urine albumin-to-creatinine ratio, blood pressure, diabetes status, medication review, symptoms, and medical history.

Use this calculator as a guide, not a diagnosis. If your eGFR is low, changing quickly, or associated with symptoms, speak with a qualified healthcare professional.