Empeiria

Estimated glomerular filtration rate

Also known as eGFR, GFR, estimated GFR, kidney function

derived index · no single molecular formula

LOINC 98979-8 code verified serum mL/min/1.73m2

unverified These explanations are written to be easy to read and have not yet been checked against a source. The ranges and measurement notes on this page show theirs.

definition unverified

Not measured directly. It is a calculation that turns your creatinine result into an estimate of how fast your kidneys are filtering, adjusted for your age and sex.

Calculated estimate of glomerular filtration rate from serum creatinine with age and sex terms; not a measured quantity.

why measured unverified

It is easier to read than creatinine on its own. The same creatinine means one thing at thirty and another at eighty. This number already takes your age into account.

It is easier to read than creatinine on its own. The same creatinine means one thing at thirty and another at eighty. This number already takes your age into account.

No clinical version written yet.

if low unverified

Filtering is reduced. A gradual decline with age is expected and normal. What matters is how far below the expected level for your age it sits, and whether it is falling over time.

Filtering is reduced. A gradual decline with age is expected and normal. What matters is how far below the expected level for your age it sits, and whether it is falling over time.

No clinical version written yet.

caveats unverified

Because it is calculated, anything that throws off creatinine throws this off too. It is unreliable in people with very high or very low muscle mass, and during a sudden illness.

Because it is calculated, anything that throws off creatinine throws this off too. It is unreliable in people with very high or very low muscle mass, and during a sudden illness.

No clinical version written yet.

What this substance is

Not a substance. eGFR is the output of an equation applied to creatinine, age and sex, so it has no chemistry, no structure and no assay -- it inherits every property of the creatinine measurement underneath it.
How it is calculated

CKD-EPI 2021 (race-free): eGFR = 142 x min(Scr/k,1)^a x max(Scr/k,1)^-1.200 x 0.9938^age x 1.012 [if female], where k = 0.7 (female) or 0.9 (male) and a = -0.241 (female) or -0.302 (male)

Derived from creatinine.

Creatinine: the measured value the equation starts from

Each molecule is drawn from ChEBI's curated 2D drawing, accepted only after its InChIKey, formula and charge matched the ChEBI release. Atom diagrams are checked against the NIST Atomic Spectra Database.

3D model · creatinine

Creatinine: the measured value the equation starts from. Generated by RDKit from ChEBI's verified structure, and accepted only because its own 3D geometry reproduces ChEBI's InChIKey. A flexible molecule takes many shapes; this is one low-energy one. Drag to rotate, scroll to zoom.

Reference ranges

Checking your own result against this range needs the running application; this is a static copy. Nothing you type anywhere in Empeiria is ever sent to a server.

all
60
normal range · mL/min/1.73m2
Applies toNormalOptimalCritical
all ≥ 60 mL/min/1.73m2 — <15

guideline limit Chronic Kidney Disease Tests and Diagnosis, National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) cited · not yet checked by a person

How it is measured

In practice

eGFR is not measured on its own. It is worked out from a blood test for creatinine, a waste product from your muscles, using a formula that also uses facts like your age and sex. Sometimes a protein called cystatin C is used too. A different test, measured GFR, puts a substance into your body and takes blood samples over several hours to see how fast your kidneys clear it. It is complex and used only in certain cases, such as before giving a kidney.

eGFR is calculated from serum creatinine (and/or cystatin C) drawn by venipuncture, entered into an estimating equation with age and sex; serum- creatinine-based equations include CKD-EPI and MDRD. Patients may be asked to fast or avoid meat for several hours before the draw because meat can affect the eGFR result. Measured GFR (mGFR) uses plasma clearance of an injected non-radiolabelled exogenous marker such as iohexol or iothalamate, with timed blood samples (e.g. five samples from 120 to 240 min, or seven from 120 to 480 min when eGFR is 40 mL/min/1.73 m2 or lower). mGFR is reserved for when eGFR is unreliable (severe malnutrition, muscle wasting, advanced liver disease, limb amputation), when a more exact value is needed for some drugs such as certain chemotherapy, and for kidney donor evaluation.

Before the test

  • Fast or avoid foods such as meat for several hours before the test if your provider asks.
  • Tell your provider about all medicines you take, but do not stop any unless told to.
  • For a measured GFR test with a urine sample, drink the amount of water your provider tells you to.

Where: laboratory

Sources: Estimated Glomerular Filtration Rate (eGFR) and GFR Tests, MedlinePlus (U.S. National Library of Medicine); GFR measurement in patients with CKD: Performance and feasibility of simplified iohexol plasma clearance techniques, PLOS ONE 2024 (PMC open access) cited · not yet checked by a person

In the lab

calculation

CKD-EPI 2021

This number is calculated, not measured. It takes your creatinine and adjusts for age and sex, because the same creatinine means different things in different people.

Estimating equation over serum creatinine, age and sex.

Why labs disagree: Which equation a lab uses changes the number. MDRD, CKD-EPI 2009 and CKD-EPI 2021 give different results for the same creatinine, enough to move some people into a different CKD stage, and the 2021 version removed the race coefficient that earlier equations included. The equation is designed for creatinine standardised to IDMS, so any error in the creatinine result carries straight into the eGFR.

Sources: Adoption of CKD-EPI (2021) for Glomerular Filtration Rate Estimation: Implications for UK Practice (2025), PMC open access; CKD-EPI Creatinine Equation (2021), National Kidney Foundation cited · not yet checked by a person

What it reports on

Associated symptoms

Conditions this marker features in

When low
  • low Long-term reduced kidney function · defining
    Under the KDIGO definition, a GFR below 60 mL/min/1.73 m² for more than 3 months indicates CKD (a raised urine albumin can also define it).
  • low Gout · supportive
    Gout is about five times more common when eGFR is 60 or below, and kidney disease is common in people with gout.
  • low High blood potassium · supportive
    Kidney function is the strongest risk factor. The risk of high potassium rises as eGFR falls, and in chronic kidney disease it is typical once eGFR is below 15.
  • low Overactive parathyroid gland · monitoring
    Kidney function is checked as part of the work-up. An eGFR or creatinine clearance below 60 mL/min is one of the guideline criteria for recommending surgery.
  • low Sudden loss of kidney function · supportive
    Part of KDIGO staging only for patients under 18: a fall in eGFR below 35 mL/min/1.73 m2 counts as stage 3. In adults the staging uses creatinine and urine output.
  • low Type 2 diabetes · monitoring
    Kidney function (eGFR, with urine albumin) is checked at least once a year in everyone with type 2 diabetes.

Ordered as part of

cmp · bmp · renal