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 11 Damage from long-term chronic kidney disease usually does not reverse. But controlling blood pressure and blood sugar can slow further loss. 2

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

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: Does the MDRD equation need your weight or height?

No. MDRD only uses creatinine, age, sex, and race. 1 The result is already given per 1.73 m² of body surface area. 1 That is why the units end in /1.73 m² . Formulas like Cockcroft-Gault do need weight, because they estimate raw creatinine clearance instead. 8

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.² Numbers below 60 for three months or more may point to chronic kidney disease.² 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.¹

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.¹ 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. A normal result is 0.7 to 1.3 mg/dL (62 to 115 µmol/L) for men and 0.5 to 0.95 mg/dL (44 to 84 µmol/L) for women.³

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 than men, so their creatinine is often lower.³ The formula multiplies by 0.742 for women.¹
Race: the original study added a 1.212 factor for Black patients.¹ In 2021, a national kidney task force recommended equations that do not use race.⁵ That is why 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).¹ The 175 constant is for creatinine measured with a method standardized to the IDMS reference method.¹

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 needed²

A low eGFR on one test does not always mean kidney disease. CKD is only diagnosed when eGFR stays below 60, or other signs of kidney damage such as protein in the urine are present, for at least 3 months.²

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.² People with little muscle, such as amputees or people who are very ill, may have low creatinine and a better-looking eGFR than is true.² Pregnancy, being over age 70, and some medicines can also shift the number.⁶ So can dehydration, which raises creatinine.³

MDRD and Newer Equations

MDRD is about as accurate as the newer CKD-EPI equation when eGFR is under 60, but it tends to underestimate higher values.⁴ The NKF-ASN Task Force now recommends that labs report the CKD-EPI 2021 equation, which does not use race.⁵ Older equations such as MDRD are still useful for comparing with past lab reports.¹⁰ For drug dosing checks, FDA guidance for drug labels uses either eGFR or creatinine clearance from the Cockcroft-Gault equation.¹²

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) ¹

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

Sex coefficient ¹

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

Race coefficient ¹

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?

In adults, a normal eGFR is usually more than 90, and eGFR goes down with age even in people without kidney disease.⁶ Average eGFR by age:

Age 20–29: 116
Age 30–39: 107
Age 40–49: 99
Age 50–59: 93
Age 60–69: 85
Age 70+: 75⁶

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.¹⁰

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.¹ The result is already given per 1.73 m² of body surface area.¹

That is why the units end in /1.73 m². Formulas like Cockcroft-Gault do need weight, because they estimate raw creatinine clearance instead.⁸

At what eGFR level do you need dialysis?

Doctors start planning for dialysis or a kidney transplant when eGFR falls below about 15 to 20.² Dialysis itself is started because of symptoms and lab results, and this often happens when eGFR is between 5 and 10.²

Signs that point toward starting include symptoms of kidney failure such as confusion, loss of appetite and itching, fluid or blood pressure that cannot be controlled, and blood chemistry problems, such as high potassium or too much acid, that medicine cannot fix.² 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 scan¹¹

Damage from long-term chronic kidney disease usually does not reverse. But controlling blood pressure and blood sugar can slow further loss.²

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) can cause acute kidney injury²
Metformin is usually not started under eGFR 45, and stopped under 30⁹
Aminoglycoside antibiotics such as gentamicin can cause acute kidney injury²
Contrast dye used in CT scans has been linked to kidney injury, so the need for the scan is weighed first²

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 and high-protein diets can raise blood creatinine without any change in the kidneys, which makes eGFR look lower.²

A cooked meat or fish meal can raise creatinine for a few hours, so it is best to wait at least 12 hours after one before the blood test.² Tell your doctor if you take creatine.

What are the symptoms of a low eGFR?

Most people feel nothing until the later stages of kidney disease.⁶ 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 eGFR and how much albumin is in your urine. For people with kidney disease, the KDIGO guideline suggests testing from once a year at the lowest-risk stages up to four or more times a year at Stage 4 or 5.²

People who take metformin should have eGFR checked at least once a year.⁹

A single low result should be repeated before calling it chronic kidney disease, because the low eGFR must last at least 3 months.²

Why was race removed from eGFR formulas?

The old MDRD race factor multiplied the eGFR of Black patients by 1.212.¹ 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.⁵ In 2021, a joint task force from the National Kidney Foundation and the American Society of Nephrology recommended that all US labs switch right away to a CKD-EPI equation without race.⁵

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 children. It was developed in children aged 1 to 16 and uses height and creatinine instead.⁷

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, people who have had an amputation, and people with very low muscle mass.² Using both creatinine and cystatin C is more accurate than creatinine alone.¹⁰

Can an eGFR be too high?

eGFR equations are less exact at high values, and MDRD tends to read low there.⁴

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.³ 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.² Doctors usually repeat the blood test and add a urine albumin-to-creatinine ratio before deciding.²

Sources

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