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Kidney function · Free tool

eGFR
calculator.

Estimate kidney function from a creatinine blood test, age and sex — using the CKD-EPI 2021 equation recommended by international kidney guidelines. Add cystatin C for a more accurate estimate.

● CKD-EPI 2021 (race-free) ● mg/dL or µmol/L ● CKD stage shown ● Nothing is stored

What the result means ↓ When it isn't accurate ↓

Dr. Nameirakpam ShantajitMBBS (SPMC Bikaner) · MS Surgery & M.Ch Urology (RIMS Imphal) · MMC Reg. No. MNP 150

Understanding the result

CKD stages

eGFR estimates how many millilitres of blood the kidneys filter each minute (per 1.73 m² body surface). Chronic kidney disease is diagnosed only when a low eGFR, or signs of kidney damage such as protein in the urine, last for at least 3 months.

Stage	eGFR	Meaning
G1	90 or more	Normal or high — CKD only if there are other signs of kidney damage
G2	60–89	Mildly decreased
G3a	45–59	Mildly to moderately decreased
G3b	30–44	Moderately to severely decreased
G4	15–29	Severely decreased — kidney specialist care
G5	Below 15	Kidney failure

🩺 Why a urologist checks eGFR

Before a CT scan or other test with contrast dye
Before stone surgery, TURP and other operations
When a stone, enlarged prostate or narrowing blocks urine flow
To choose and dose medicines safely
To follow kidney function after treatment

📈 What to do with your number

A single low value can be temporary — it is often repeated
Bring your past reports: the trend tells the most
A urine test for protein completes the picture
Control blood pressure and sugar, drink sensibly, avoid unprescribed painkillers
Discuss any result below 60 with your doctor

Limitations

When eGFR isn't accurate

⚡

Sudden kidney injury

When creatinine is rising or falling quickly (acute kidney injury, after a blockage is relieved), the estimate lags behind real function.

💪

Unusual muscle mass

Body-builders, amputees, very thin or bed-bound people, and high-protein or creatine supplements can make creatinine misleading. Cystatin C helps here.

🤰

Pregnancy & children

The equation is not designed for pregnancy or for children under 18 — different methods are used.

For students & doctors — the equation used

CKD-EPI 2021 (creatinine): eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × 1.012 [if female] κ = 0.7 (F) / 0.9 (M) · α = −0.241 (F) / −0.302 (M) · Scr in mg/dL CKD-EPI 2021 (creatinine + cystatin C): eGFR = 135 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−0.544 × min(Scys/0.8, 1)^−0.323 × max(Scys/0.8, 1)^−0.778 × 0.9961^Age × 0.963 [if female] κ = 0.7 (F) / 0.9 (M) · α = −0.219 (F) / −0.144 (M)

Inker LA et al., N Engl J Med 2021. Creatinine µmol/L ÷ 88.4 = mg/dL. Results are rounded to whole numbers.

Questions

Frequently asked questions

Is eGFR the same as creatinine?

No. Creatinine is the blood test; eGFR is calculated from it together with your age and sex, and is a better guide to how well the kidneys filter.

My eGFR is 75. Do I have kidney disease?

Not necessarily. Values of 60–89 are common, especially with age. It counts as chronic kidney disease only if there are other signs of kidney damage, such as protein in the urine, for 3 months or more.

Can eGFR improve?

Yes, sometimes — for example after dehydration is corrected or a blockage (stone, enlarged prostate) is treated. Long-standing damage usually doesn't reverse, but its progress can often be slowed.

Should I drink a lot of water before the test?

No special preparation is needed. Drink normally; being dehydrated can make the result look worse than it is.

Book a consultation

NAM Consultants, Singjamei: mornings daily 6:00–9:30 AM (Mar–Oct) / 6:30–9:30 AM (Nov–Feb), evenings 4–6 PM Mon–Sat · Raj Medicity Hospital: Mon–Sat 11 AM–1 PM

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Medically reviewed by Dr. Nameirakpam Shantajit, M.Ch Urology (MMC Reg. No. MNP 150) · Last reviewed: 22 October 2026

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