Estimate your Glomerular Filtration Rate (GFR), a measure of kidney function, using the MDRD formula. This is informational only — always consult a doctor for medical decisions.
A GFR (Glomerular Filtration Rate) Calculator estimates how well the kidneys are filtering waste from the blood, based on factors like serum creatinine level, age, gender, and sometimes race or body size. GFR is one of the most important clinical indicators of kidney function, used by doctors to detect, stage, and monitor chronic kidney disease and other renal conditions.
Common formulas include the CKD-EPI and MDRD equations, both of which use serum creatinine along with age and gender (and sometimes race, depending on the specific formula version used) to estimate GFR in milliliters per minute per 1.73 square meters of body surface area, a standardized way of comparing kidney function across people of different body sizes.
Enter your serum creatinine level (from a blood test), age, and gender. The calculator estimates your GFR and indicates which chronic kidney disease stage, if any, that value corresponds to, ranging from normal kidney function to varying degrees of impairment.
Example 1: A 45-year-old man with a serum creatinine of 1.0 mg/dL typically has an estimated GFR in the normal range, above 90 mL/min/1.73m², indicating healthy kidney filtration function.
Example 2: A 65-year-old woman with a serum creatinine of 1.8 mg/dL typically has a significantly lower estimated GFR, potentially falling into a moderate chronic kidney disease stage, warranting further medical evaluation and monitoring.
Kidney function naturally tends to decline gradually with age even in healthy individuals, so GFR formulas incorporate age to provide a more accurate estimate that accounts for this normal physiological trend rather than falsely flagging normal age-related decline as disease.
A GFR of 90 or above is generally considered normal kidney function, with values between 60 and 89 sometimes indicating mildly reduced function (especially if other kidney damage markers are present), and progressively lower values indicating more significant kidney impairment through the recognized chronic kidney disease stages.
Directly measuring GFR requires complex clinical procedures involving injecting and tracking specific filtration markers, which is impractical for routine screening, so estimated GFR formulas using a simple blood creatinine test provide a practical, widely accessible alternative for everyday clinical use.
Yes, muscle mass, certain medications, dehydration, and diet (particularly high meat consumption before testing) can all influence creatinine levels independent of actual kidney function, which is why doctors interpret GFR results alongside other clinical information rather than in isolation.
Chronic kidney disease is typically classified into five stages based on GFR ranges, from Stage 1 (normal or high GFR with other evidence of kidney damage) through Stage 5 (GFR below 15, indicating kidney failure), helping guide treatment decisions and monitoring frequency.
Different formulas (such as CKD-EPI versus MDRD) use somewhat different mathematical approaches and were validated on different study populations, so it's normal for them to produce slightly different estimates, though both aim to approximate the same underlying kidney function.
No, while this tool provides a useful estimate based on standard formulas, a doctor's full clinical assessment, including trends over multiple tests, other lab markers, and overall health context, is essential for accurately diagnosing and managing any kidney function concerns.
Depending on the underlying cause, certain lifestyle changes such as managing blood pressure and diabetes, reducing salt intake, staying hydrated, and avoiding kidney-stressing medications can help slow further decline, though established kidney damage often cannot be fully reversed, making early detection and management particularly important.
Chronic kidney disease often progresses silently with few noticeable symptoms until it reaches advanced stages, so regular GFR monitoring, especially for people with risk factors like diabetes or high blood pressure, allows earlier intervention that can meaningfully slow disease progression.
Doctors often recommend annual or more frequent GFR testing for people with diabetes, hypertension, or a family history of kidney disease, allowing trends to be tracked over time rather than relying on a single isolated measurement.
This standardization allows fair comparison of kidney filtration capacity between people of different body sizes, since a larger body naturally has a larger kidney filtration capacity in absolute terms, and the normalized figure removes that size effect.
Yes, since creatinine is a muscle metabolism byproduct, people with unusually high or low muscle mass relative to average can get somewhat skewed GFR estimates, which is why doctors sometimes use alternative markers like cystatin C for these specific populations.