Yes, sometimes. A low eGFR from a short-term problem often improves once that problem is fixed. Common causes are: Dehydration or vomiting Infection Medicines like NSAIDs (ibuprofen, naproxen) Contrast dye from a scan Damage from long-term chronic kidney disease usually does not reverse. But controlling blood pressure, blood sugar, and weight can slow or stop further loss.

MDRD GFR Calculator - mg/dL or µmol/L, Sex & Race Factors

Q: What is a normal eGFR for my age?

Healthy young adults usually have an eGFR near 100 to 120 mL/min/1.73 m² . Filtering speed slowly drops with age, about 1 mL/min per year after age 40. Age 20–29: around 100–120 Age 40–49: around 90–100 Age 60–69: around 80–90 Age 70+: often 70–80 A number a bit under 90 in an older adult is common and may not mean disease. Doctors look at trends over time, not one test.

Q: How do you convert creatinine from µmol/L to mg/dL?

Divide by 88.42 . mg/dL = µmol/L ÷ 88.42 To go the other way, multiply mg/dL by 88.42. Example: 100 µmol/L ÷ 88.42 = 1.13 mg/dL . Most labs in the United States report mg/dL. Labs in Canada, Europe, and Australia usually report µmol/L.

Q: How often should eGFR be tested?

It depends on your risk: Healthy adults: with routine bloodwork, about every 1 to 3 years Diabetes or high blood pressure: at least once a year eGFR 45–59: about twice a year eGFR 30–44: about every 3 to 4 months eGFR under 30: every 1 to 3 months A single low result should be repeated in about 3 months before calling it chronic kidney disease.

Introduction

This MDRD Calculator estimates how well your kidneys clean your blood. The result is called eGFR, which stands for estimated glomerular filtration rate. It is measured in mL/min/1.73 m².

The MDRD equation uses four things: your serum creatinine level, your age, your sex, and (optionally) whether you are Black or African American. Creatinine is a waste product your muscles make. Healthy kidneys filter it out into urine. When creatinine builds up in the blood, it can mean the kidneys are not filtering well.

To use the tool, pick your sex, type your age, and enter your creatinine from a recent blood test. You can enter creatinine in mg/dL or µmol/L. The result updates as you type and shows your eGFR, what range it falls in, a gauge, and a step-by-step solution so you can see how the number was found.

A higher eGFR means better kidney function. An eGFR of 90 or above is normal. Numbers below 60 for three months or more may point to chronic kidney disease. This tool is for adults 18 and older and is meant for learning. It does not replace advice from your doctor. Always talk to a health care provider about your results.

How to use our MDRD GFR Calculator

Enter your sex, age, and serum creatinine level. The calculator gives you an estimated GFR (eGFR) in mL/min/1.73 m², a kidney function rating, and a step-by-step look at the math.

Sex: Tap Female or Male. The MDRD formula uses a 0.742 factor for females.

Age: Type your age in whole years. It must be between 18 and 120. This formula is for adults only.

Race / Ethnicity (optional): Tap Black / African American or Other / Not Specified. Picking Black applies a 1.212 factor. If you leave it blank, no change is made. Tap a selected button again to clear it.

Serum Creatinine: Type the creatinine value from your blood test. Pick mg/dL or µmol/L from the drop-down, and the number switches units for you. Normal is about 0.7–1.3 mg/dL (62–115 µmol/L).

Press Calculate to see your eGFR, the gauge chart, and where your result falls in the kidney function bands. Press Copy Result to save it, or Reset to start over.

What Is the MDRD eGFR Equation?

The MDRD equation estimates how well your kidneys clean your blood. MDRD stands for Modification of Diet in Renal Disease, the study that created the formula. The answer it gives is called eGFR, or estimated glomerular filtration rate. It is measured in mL/min/1.73 m², which means how many milliliters of blood your kidneys filter each minute, adjusted for an average body size.

What Goes Into the Formula

The 4-variable MDRD equation uses four things:

Serum creatinine: a waste product from muscle that healthy kidneys remove. When kidneys slow down, creatinine builds up in the blood.
Age: kidney filtering slowly drops as people get older.
Sex: women usually have less muscle, so the formula multiplies by 0.742.
Race: the original study added a 1.212 factor for Black patients. Many labs no longer use this factor, so it is optional here.

The formula is: eGFR = 175 × (creatinine in mg/dL)^−1.154 × (age)^−0.203 × 0.742 (if female) × 1.212 (if Black). The 175 constant is used when the lab creatinine test is IDMS-standardized, which most modern labs are.

What the Numbers Mean

Doctors use eGFR to sort kidney function into stages of chronic kidney disease (CKD):

90 or higher: normal or high filtering
60–89: mildly reduced
45–59: mild to moderate loss
30–44: moderate to severe loss
15–29: severely reduced
Under 15: kidney failure, and dialysis or a transplant may be needed

A low eGFR on one test does not always mean kidney disease. CKD is only diagnosed when eGFR stays below 60 for at least three months, or when other signs like protein in the urine show up.

Things That Can Change the Result

Creatinine comes from muscle, so the number can be off for some people. Very muscular people, bodybuilders, and those who eat a lot of meat may have higher creatinine and a lower-looking eGFR. People with little muscle, such as older adults, amputees, or people who are very ill, may have low creatinine and a better-looking eGFR than is true. Pregnancy, some medicines, and dehydration can also shift the number.

MDRD and Newer Equations

MDRD works best for eGFR values under 60 and tends to underestimate higher values. Because of this, most labs now report the CKD-EPI 2021 equation, which is more accurate at normal kidney function and does not use race. MDRD is still widely used and is helpful for drug dosing checks and for comparing to older lab reports.

Note: This tool is for adults 18 and older and does not replace medical advice. Talk with a doctor about your lab results and what they mean for you.

Formulas used

MDRD 4-variable eGFR (IDMS re-expressed)

eGFR = 175 \times S_{cr}^{-1.154} \times \text{Age}^{-0.203} \times k_{sex} \times k_{race}

Sex coefficient

k_{sex} = \begin{cases} 0.742 & \text{female} \\ 1 & \text{male} \end{cases}

Race coefficient

k_{race} = \begin{cases} 1.212 & \text{Black / African American} \\ 1 & \text{otherwise} \end{cases}

Creatinine unit conversion (µmol/L to mg/dL)

S_{cr}\,[\text{mg/dL}] = \frac{S_{cr}\,[\mu\text{mol/L}]}{88.42}

Creatinine unit conversion (mg/dL to µmol/L)

S_{cr}\,[\mu\text{mol/L}] = S_{cr}\,[\text{mg/dL}] \times 88.42

Gauge fill percentage

\text{Gauge \%} = \min\left(\max\left(\frac{eGFR}{120} \times 100,\ 0\right),\ 100\right)

Frequently asked questions

What is a normal eGFR for my age?

Healthy young adults usually have an eGFR near 100 to 120 mL/min/1.73 m². Filtering speed slowly drops with age, about 1 mL/min per year after age 40.

Age 20–29: around 100–120
Age 40–49: around 90–100
Age 60–69: around 80–90
Age 70+: often 70–80

A number a bit under 90 in an older adult is common and may not mean disease. Doctors look at trends over time, not one test.

How do you convert creatinine from µmol/L to mg/dL?

Divide by 88.42.

mg/dL = µmol/L ÷ 88.42

To go the other way, multiply mg/dL by 88.42.

Example: 100 µmol/L ÷ 88.42 = 1.13 mg/dL. Most labs in the United States report mg/dL. Labs in Canada, Europe, and Australia usually report µmol/L.

Does the MDRD equation need your weight or height?

No. MDRD only uses creatinine, age, sex, and race. The result is already adjusted to a standard body size of 1.73 m², which is the average adult body surface area.

That is why the units end in /1.73 m². Formulas like Cockcroft-Gault do need weight, because they estimate raw creatinine clearance instead.

At what eGFR level do you need dialysis?

Doctors usually start talking about dialysis when eGFR falls below 15. Most people start when the number drops near 10, or sooner if they have bad symptoms.

Symptoms that push the decision include swelling that will not go away, nausea, trouble breathing, confusion, and high potassium. Some people with an eGFR of 12 feel fine and wait. The number alone does not decide it.

Can eGFR go back up?

Yes, sometimes. A low eGFR from a short-term problem often improves once that problem is fixed. Common causes are:

Dehydration or vomiting
Infection
Medicines like NSAIDs (ibuprofen, naproxen)
Contrast dye from a scan

Damage from long-term chronic kidney disease usually does not reverse. But controlling blood pressure, blood sugar, and weight can slow or stop further loss.

What medicines are risky when eGFR is low?

Several common drugs need a lower dose or must be stopped when kidneys slow down:

NSAIDs (ibuprofen, naproxen) cut blood flow to the kidneys
Metformin is usually not started under eGFR 45, and stopped under 30
Some antibiotics like gentamicin and vancomycin
Contrast dye used in CT scans

Never stop a prescribed drug on your own. Ask your doctor or pharmacist to check your doses against your eGFR.

Do creatine supplements raise creatinine and lower eGFR?

Yes, often. Creatine supplements break down into creatinine, so blood creatinine can rise. That makes eGFR look lower even though the kidneys are fine.

Heavy weight training and eating a lot of cooked meat can do the same thing. Stop creatine and avoid heavy meat meals for a few days before a blood test, and tell your doctor if you take it.

What are the symptoms of a low eGFR?

Most people feel nothing until eGFR falls under about 30. That is why kidney disease is called a silent condition.

Later signs include:

Tiredness and weakness
Swollen ankles, feet, or face
Peeing more at night
Foamy urine
Itchy skin
Poor appetite or nausea
Trouble sleeping

A blood and urine test is the only way to catch it early.

How often should eGFR be tested?

It depends on your risk:

Healthy adults: with routine bloodwork, about every 1 to 3 years
Diabetes or high blood pressure: at least once a year
eGFR 45–59: about twice a year
eGFR 30–44: about every 3 to 4 months
eGFR under 30: every 1 to 3 months

A single low result should be repeated in about 3 months before calling it chronic kidney disease.

Why was race removed from eGFR formulas?

The old race factor raised the eGFR of Black patients by about 21%. That higher number could delay a diagnosis, a specialist referral, or a place on a transplant list.

Race is a social label, not a biological measure of kidney function. In 2021, a joint task force from the National Kidney Foundation and the American Society of Nephrology recommended a race-free equation. Most labs now report CKD-EPI 2021 without race.

Why is MDRD not used for children?

The MDRD study only included adults, so its math does not fit growing bodies. Children have less muscle, so their creatinine is naturally low, and MDRD would give a wrong answer.

Doctors use the Bedside Schwartz equation for kids under 18. It uses height and creatinine instead.

What is a cystatin C test and why is it used?

Cystatin C is another waste protein the kidneys filter. Unlike creatinine, it does not depend much on muscle, diet, or age.

Doctors order it when creatinine may mislead, such as in bodybuilders, amputees, very thin people, or older adults with little muscle. Combining creatinine and cystatin C usually gives the most accurate eGFR.

Can an eGFR be too high?

Most equations, including MDRD, just report anything over 90 or 120 as normal because they are not exact in that range.

A truly high number can mean hyperfiltration, where the kidneys work too hard. It can show up early in diabetes, obesity, or pregnancy, and it may lead to damage later. It can also simply mean low muscle mass. Talk to a doctor if your number seems unusually high.

Does drinking more water improve eGFR?

Only a little, and only if you were dry. Dehydration raises creatinine and lowers eGFR, so normal hydration brings the number back to its true level.

Drinking huge amounts of water does not repair damaged kidneys and can be harmful for people with advanced kidney or heart disease. Aim for normal thirst-based drinking unless your doctor says otherwise.

Does a low eGFR always mean chronic kidney disease?

No. One low reading can come from dehydration, illness, a big protein meal, hard exercise, or a medicine.

Chronic kidney disease is diagnosed when the eGFR stays under 60 for at least 3 months, or when other damage signs show up, such as protein (albumin) in the urine. Doctors usually repeat the blood test and add a urine albumin-to-creatinine ratio before deciding.

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