eGFR Calculator: Kidney Function Estimate (MDRD)

What does your result mean?

This is your estimated glomerular filtration rate (eGFR) in mL/min/1.73 m².

If you are:

1. In range: Your kidneys are filtering at an expected level for adults (commonly ~90–120 mL/min/1.73 m²; ≥60 without albumin in urine is often acceptable in older adults). Keep steady hydration, maintain a balanced diet, and continue routine checks of blood pressure, blood sugar, and urine albumin.
2. Below range: A lower eGFR (especially <60) suggests reduced kidney filtration. Recheck labs, including urine albumin-to-creatinine ratio, review medications (avoid frequent NSAIDs), prioritize blood pressure/sugar control, limit excess salt, and discuss follow-up with your clinician.
3. Above range: Very high eGFR (often >120) can reflect hyperfiltration (seen with early diabetes, obesity, high-protein intake, or pregnancy). Recheck when well hydrated, consider urine albumin and glucose/A1c screening, and focus on weight, blood pressure, and moderate protein intake.

Note: Targets are guides, not medical advice. Adjust based on your symptoms, known conditions, and clinician recommendations.

How is this calculated?

Evidence baseline:

Uses the simplified MDRD (4‑variable) equation to estimate filtration normalized to a standard body surface area of 1.73 m²: eGFR = 175 × (serum creatinine in mg/dL)^(-1.154) × (age in years)^(-0.203). Based on established scientific principles.

Sized to you:

The estimate scales with your serum creatinine (mg/dL or converted from µmol/L ÷ 88.4) and age. It is indexed to 1.73 m² rather than your actual body size; very high or low muscle mass can shift creatinine and thus eGFR.

Activity adjustment:

The calculation itself doesn’t add or subtract for activity, but hard exercise, dehydration, creatine use, or a large meat meal within 24–48 hours can raise creatinine and transiently lower eGFR. Testing when rested and well hydrated gives a steadier reading.

Environment & day-to-day:

Illness, pregnancy, and some drugs (e.g., trimethoprim, cimetidine, certain antibiotics) can raise creatinine independent of true GFR. Lab assay variation and hydration status also introduce small shifts from day to day.

Why a range?

Biological and assay variability and equation error mean any single eGFR has uncertainty (~±10–20%). A range reflects this natural fluctuation and age-related differences rather than one “perfect” number.

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