eGFR Calculator Guide: What Your Kidney Function Score Means

What Is eGFR?

eGFR stands for Estimated Glomerular Filtration Rate. It measures how much blood your kidneys filter per minute, adjusted for body surface area. The result is reported in milliliters per minute per 1.73 square meters (mL/min/1.73m²).

Your kidneys contain about one million tiny filtering units called nephrons. Each nephron has a glomerulus — a small knot of capillaries that filters waste products, excess water, and electrolytes out of the blood. eGFR estimates the total filtration capacity of all functioning glomeruli combined.

A healthy young adult has an eGFR of roughly 90–120 mL/min/1.73m². Values above 60 are generally considered adequate kidney function. Sustained values below 60 for three or more months — or the presence of kidney damage markers like protein in the urine — define Chronic Kidney Disease according to KDIGO (Kidney Disease: Improving Global Outcomes) guidelines.

The CKD-EPI Equation: How eGFR Is Calculated

eGFR is not measured directly. It is estimated from a blood test for serum creatinine— a waste product your muscles produce at a roughly constant rate. The kidneys filter creatinine out; when filtration declines, creatinine rises in the blood.

The current clinical standard is the 2021 CKD-EPI equation, developed by the Chronic Kidney Disease Epidemiology Collaboration. It uses:

• Serum creatinine (mg/dL)
• Age (years)
• Sex assigned at birth (male or female)

The 2021 update removed the race variable that was previously used to adjust results for Black patients. The National Kidney Foundation and the American Society of Nephrology jointly recommended this change in 2021 to eliminate race-based differences in clinical decision-making and ensure equitable care.

CKD-EPI replaced the older MDRD (Modification of Diet in Renal Disease) equation because it is more accurate across the full range of eGFR values — particularly important for values above 60, where MDRD tends to underestimate kidney function.

Some labs also report cystatin C–based eGFR (eGFRcys), which uses a different filtration marker. CKD-EPI equations combining both creatinine and cystatin C are the most accurate for confirming CKD stage.

CKD Stages by eGFR (Stages 1–5)

KDIGO classifies CKD into five stages based on eGFR. Stage is assigned only when kidney damage persists for three months or more — a single low reading does not confirm CKD.

According to the National Kidney Foundation, most people with CKD Stages 1–3 have no symptoms. That silence is part of why 90% of CKD patients are undiagnosed.

Key eGFR Statistics You Should Know

The scale of kidney disease in the US is significant:

• The CDC estimates 37 million Americans (about 15% of adults) have CKD — more people than have diabetes.
• 9 out of 10 adults with CKD do not know they have it, per the CDC’s Chronic Kidney Disease Surveillance System.
• 1 in 3 adults with diabetes has CKD, and 1 in 5 adults with high blood pressure has CKD. These two conditions are the leading causes of kidney failure.
• After age 40, eGFR naturally declines at roughly 1 mL/min/1.73m² per year. A 70-year-old may have an eGFR of 70 with perfectly healthy kidneys.
• People with CKD Stage 3–4 progress to kidney failure at a rate of roughly 1–2% per year, though this varies widely by cause, blood pressure control, and proteinuria levels.
• CKD is the 9th leading cause of death in the United States, accounting for more than 52,000 deaths per year, per the CDC.

eGFR Decline Benchmarks

KDIGO defines rapid CKD progression as a sustained eGFR decline of more than 5 mL/min/1.73m² per year. A decline of more than 25% from baseline within a year also qualifies as significant progression.

What Affects Your eGFR Reading?

eGFR can fluctuate based on factors unrelated to true kidney function. Understanding these helps you interpret results more accurately:

• Muscle mass: Creatinine is produced by muscles. Athletes and people with high muscle mass may have elevated creatinine and slightly lower calculated eGFR, even with normal kidneys. Low muscle mass (older adults, malnutrition) can produce falsely elevated eGFR.
• Dehydration: Reduces blood flow to the kidneys temporarily, raising creatinine and lowering eGFR. A single low reading may reflect dehydration rather than chronic kidney damage.
• Diet: Eating a large amount of cooked meat raises creatinine for several hours. Some labs request patients avoid meat before testing.
• Medications: NSAIDs (ibuprofen, naproxen), ACE inhibitors, ARBs, certain antibiotics, and contrast dye used in imaging can acutely reduce eGFR. Metformin, creatine supplements, and trimethoprim can artificially raise creatinine.
• Age: eGFR naturally declines with age, so a 75-year-old with an eGFR of 65 may have normal age-adjusted kidney function.
• Pregnancy: eGFR increases during pregnancy, so normal ranges differ. Low eGFR in pregnancy may indicate preeclampsia.

eGFR vs Creatinine vs BUN: How Kidney Tests Differ

eGFR is considered the single best marker of overall kidney function for clinical decision-making. However, UACR (urine protein) is equally important for staging CKD and predicting progression — two people with the same eGFR can have very different risks depending on their proteinuria level.

5 Steps to Protect Your Kidney Function

For people with CKD or risk factors, these evidence-based interventions slow progression:

1. Control blood pressure below 130/80 mmHg. Hypertension is both a cause and a consequence of kidney disease. ACE inhibitors and ARBs are preferred antihypertensives for CKD because they reduce pressure inside the glomeruli, slowing filtration damage.
2. Manage blood sugar if diabetic. Targeting HbA1c below 7% in most diabetic patients with CKD reduces the risk of kidney damage progression. The SGLT2 inhibitor class (canagliflozin, dapagliflozin) has shown specific kidney-protective benefits beyond glucose control.
3. Reduce dietary sodium and protein.High sodium raises blood pressure and increases filtration pressure. Excess protein intake generates more urea and creatinine waste for damaged kidneys to handle. KDIGO recommends limiting protein to 0.6–0.8 g/kg/day for CKD Stage 3–5 patients not on dialysis.
4. Avoid nephrotoxic medications. NSAIDs (ibuprofen, naproxen, aspirin in high doses), certain antibiotics (aminoglycosides), and imaging contrast agents can cause acute kidney injury. Always disclose your eGFR and CKD status to every provider and pharmacist.
5. Stop smoking and maintain a healthy weight.Smoking reduces blood flow to the kidneys and accelerates CKD progression. Obesity is independently associated with CKD development and progression. Even modest weight loss (5–10% of body weight) reduces proteinuria.

Frequently Asked Questions

What is a normal eGFR?

A normal eGFR is 60 mL/min/1.73m² or above. Values of 90 or higher indicate normal kidney function. An eGFR between 60 and 89 is considered mildly reduced but not necessarily CKD unless accompanied by other markers of kidney damage. An eGFR below 60 for 3 or more months meets the criterion for Chronic Kidney Disease.

What does a low eGFR mean?

A low eGFR (below 60) means your kidneys are filtering blood less effectively than normal. The lower the number, the less kidney function remains. An eGFR of 15 or below indicates kidney failure (CKD Stage 5), where dialysis or a transplant may be needed. Values between 15 and 59 indicate varying levels of CKD (Stages 3 and 4). Always consult a nephrologist for interpretation.

Can eGFR improve?

Yes, eGFR can improve, particularly in early-stage CKD. Managing blood pressure (target below 130/80), controlling blood sugar in diabetes, reducing sodium intake, stopping smoking, and maintaining a healthy weight can all slow decline or allow modest recovery. However, significant improvement is uncommon in advanced CKD. A single low eGFR reading may also reflect temporary factors like dehydration — confirmation over 3+ months is required for a CKD diagnosis.

What is the CKD-EPI equation?

The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation is the current gold standard for estimating GFR. It uses serum creatinine, age, and sex to calculate eGFR. The 2021 CKD-EPI equation removed the race variable (previously used to adjust for Black patients) and is recommended by KDIGO and the National Kidney Foundation. It is more accurate than the older MDRD equation, especially for eGFR values above 60.

How often should eGFR be checked?

For healthy adults, eGFR is typically checked as part of a standard metabolic panel at annual physicals. People with diabetes, high blood pressure, or a family history of kidney disease should have eGFR checked at least once a year. Those already diagnosed with CKD should be monitored more frequently — every 3 to 6 months for Stage 3, and every 1 to 3 months for Stages 4 and 5 — per KDIGO guidelines.

How does eGFR differ from creatinine and BUN?

Creatinine is a waste product filtered by the kidneys; elevated creatinine suggests reduced filtration. BUN (Blood Urea Nitrogen) measures another waste product and can be affected by diet and dehydration. eGFR is calculated from creatinine (plus age and sex) and is standardized to body surface area, making it easier to interpret across different people. eGFR is considered the best single marker of kidney function for clinical decisions.