GFR Calculator

Normal eGFR is above 90 ml/min/1.73 m² for adults under 60. Healthy older adults (60+) often have lower eGFR — 75–90 — without indicating disease, since kidney function declines gradually with age. Below 60 sustained for 3+ months indicates chronic kidney disease (CKD). Above 90 with no other markers (proteinuria, hematuria, structural issues) is normal. eGFR is calculated from blood creatinine using equations like CKD-EPI 2021. The result is reported per 1.73 m² body surface area for standardisation. A single low result doesn't diagnose disease — repeat testing and full kidney evaluation are needed.

eGFR is estimated from serum creatinine, age, and sex using the CKD-EPI 2021 equation. The formula is complex (involves age, sex, creatinine, and constants), but calculators do it instantly. Higher creatinine means lower eGFR. Example: a 50-year-old man with creatinine 1.0 mg/dL has eGFR around 86 — within normal range for his age. A 70-year-old woman with creatinine 1.2 mg/dL has eGFR around 50 — indicating moderate kidney function reduction. Cystatin C-based eGFR is an alternative for cases where creatinine is unreliable (very low muscle mass, amputees, body builders).

eGFR below 60 sustained for 3 months or more meets the definition of chronic kidney disease (CKD). Stages: G3a (eGFR 45–59), G3b (30–44), G4 (15–29), G5 (below 15, kidney failure or end-stage renal disease). Above 60 with proteinuria still indicates CKD. eGFR 50–60 is mild kidney function reduction — common in older adults. The lower the eGFR, the greater the risk of cardiovascular events, electrolyte imbalances, and progression to end-stage renal disease. Patients with eGFR below 60 should see a nephrologist for evaluation, blood pressure control, and management of risk factors like diabetes and hypertension.

Not always. eGFR can be transiently low due to dehydration, recent strenuous exercise, certain medications (NSAIDs, ACE inhibitors), high-protein meals before testing, or measurement variability. A single low eGFR should be repeated. CKD diagnosis requires sustained low eGFR (below 60) for at least 3 months along with other kidney markers (proteinuria, hematuria, structural abnormalities on imaging). Older adults often have eGFR in the 60–75 range without active disease — kidney function naturally declines with age. Always interpret eGFR alongside urine tests, imaging, and clinical context. Don't panic over a single result.

Yes. Dehydration concentrates creatinine in the blood, raising the value and lowering the calculated eGFR temporarily. After rehydration, eGFR returns to baseline. This is why we recheck low eGFR after a few weeks rather than diagnosing CKD on a single test. Other reversible causes: recent intense exercise, high-protein meals, certain medications, fever, or acute illness. For accurate baseline kidney function testing, drink normally, avoid intense exercise the day before, and avoid high-protein meals for 12 hours. If your first low eGFR was during illness or after a heavy meal, the repeat test will likely look better.

The 2021 CKD-EPI equation removed the race-based correction factor used previously. Earlier equations applied a 'multiplier' for Black patients, raising their eGFR by about 16%, based on assumptions about muscle mass and creatinine production that aren't biologically accurate. Studies showed the race correction delayed diagnosis of kidney disease in Black patients and contributed to inequities in transplant referrals. The 2021 equation uses creatinine plus cystatin C (where available) for more accurate, race-neutral estimation. The change affects millions of patients globally and aligns kidney care with current understanding that race is a social, not biological, classifier.