What is the normal eGFR range?
An eGFR ≥60 mL/min/1.73m² is generally considered within the normal range, though values 60–89 indicate mildly decreased function. CKD is defined as eGFR <60 persisting for ≥3 months, or eGFR ≥60 with other markers of kidney damage. eGFR naturally declines with age.
Why does sex affect eGFR?
The CKD-EPI equation incorporates a sex-specific factor because women have lower muscle mass on average than men of the same age, producing less creatinine. For the same serum creatinine value, a woman's eGFR is estimated higher than a man's because the lower baseline creatinine suggests better-than-average kidney function relative to her muscle mass.
Does an eGFR of 60 always mean kidney disease?
No. It can be consistent with chronic kidney disease if it persists or if other markers of kidney damage are present, but one isolated result near 60 does not automatically confirm CKD. Age, repeat testing, urine albumin, and the wider clinical picture all matter.
Is eGFR the same as creatinine clearance?
No. They are related but not identical. eGFR is a body-surface-area-standardised estimate of kidney filtration, while creatinine clearance is a different measure often used in drug-dosing contexts. Some pages compare both, but they are not interchangeable outputs.
Why is repeat testing needed before CKD is diagnosed?
Chronic kidney disease is defined by persistence over time, not by one isolated lab result. A single low eGFR may reflect temporary illness, dehydration, medication effects, or lab variation, so clinicians usually repeat testing and look for other markers such as albuminuria before confirming CKD.
What is the difference between eGFR and creatinine clearance in practice?
eGFR is commonly used for general kidney-function interpretation and staging, while creatinine clearance is often used in medication dosing or when a clinician wants a different filtration estimate. They are related numbers, but they answer slightly different clinical questions and should not be treated as the same thing.
What does an eGFR of 45 mean?
An eGFR around 45 is in the G3a range. On its own it suggests mild to moderate reduction in filtration, but whether that means confirmed CKD depends on persistence over at least 3 months and whether urine ACR or other kidney-damage markers are abnormal.
What does an eGFR of 90 mean if protein is present in the urine?
An eGFR of 90 can still be compatible with CKD if persistent albuminuria or other kidney-damage markers are present. That is why preserved filtration does not automatically rule out kidney disease.
Can dehydration lower eGFR temporarily?
Yes. Dehydration, intercurrent illness, some medications, and other short-term factors can increase creatinine temporarily and lower a creatinine-based eGFR estimate. That is one reason repeat testing is often needed before a chronic diagnosis is made.
Why do some labs report creatinine in mg/dL and others in µmol/L?
Both are standard creatinine units. Many UK and European labs use µmol/L, while many US labs use mg/dL. The calculator converts between them before applying the CKD-EPI 2021 equation.
What urine ACR is considered high?
In broad terms, ACR below 3 mg/mmol is A1, 3 to 30 mg/mmol is A2, and above 30 mg/mmol is A3. Higher albuminuria categories usually signal more kidney-damage risk when the abnormality persists.
When should cystatin C be considered?
Cystatin C can be useful when creatinine-based eGFR is borderline, especially in the 45 to 59 range without another kidney-damage marker, or when muscle mass makes creatinine harder to interpret. It is not needed for every person, but it can clarify uncertainty.
What does the combined creatinine-cystatin C eGFR mean?
When cystatin C is entered, the calculator adds the 2021 CKD-EPI creatinine-cystatin C estimate. This does not replace clinical judgement, but it can give a more useful confirmation estimate when creatinine alone may be distorted or when the eGFR is close to a decision threshold.
When should I see a nephrologist?
That depends on the overall picture, but markedly reduced eGFR, very high urine ACR, progressive decline, resistant hypertension, or uncertainty about the cause are common reasons for specialist review. A clinician can judge the urgency from the full lab and medical context.
Is this a normal GFR by age calculator?
It helps with that question, but it is not a simple age chart. The calculator estimates current eGFR and explains how age, creatinine, and urine ACR affect interpretation, because normal ageing and CKD can overlap in the same headline number.
Can I use this as a kidney function calculator after one blood test?
Yes, as an educational interpretation tool. What it should not be used for is self-diagnosing chronic kidney disease from a single isolated result without repeat testing, urine findings, or clinical review.
