Kidneys and electrolytes · Blood

eGFR

A calculated estimate of the kidneys' filtration rate from creatinine, age and sex; the measure of kidney function.

At a glance

Measured in blood
In 13 test panels
No special preparation

Explanation

eGFR: what is measured?

The eGFR (estimated glomerular filtration rate) is not a measurement but a calculation. Using the CKD-EPI formula, the laboratory converts the creatinine in the blood into the number of milliliters of blood the kidneys filter per minute, corrected for age and sex and for an average body surface area. This makes a creatinine value comparable between a young man with a lot of muscle and an older woman with little muscle. An eGFR of 90 or higher fits normal kidney function; the lower the number, the less the kidneys filter. According to the Dutch GP guideline (NHG), the eGFR together with albumin in the urine is the basis for diagnosing and classifying kidney damage.

What can it detect?

Reduced kidney function and its stage according to the Dutch GP guideline (NHG) on chronic kidney damage
Increased risk of cardiovascular disease: a lower eGFR counts toward cardiovascular risk
The need to adjust the dose of medicines that are excreted by the kidneys

Result

What does the result mean?

eGFR too high

A high eGFR (90 or higher) is normal and means the kidneys filter well. A strikingly high value says little: above 90 the formula is inaccurate and the result depends mainly on little muscle mass, pregnancy or a protein-rich meal. Only in diabetes can long-term excessive filtration be an early sign of strain on the kidneys; even then, albumin in the urine is what mainly counts.

eGFR too low

The NHG guideline divides the eGFR into stages. A value of 60 to 89 is mildly reduced and, in people without protein in the urine or other abnormalities, is not yet kidney damage; at older ages this is common. Chronic kidney damage is present if the eGFR stays below 60 on repeated testing over a period of at least 3 months, or if there is too much albumin in the urine. An eGFR of 45 to 59 is mildly to moderately reduced, 30 to 44 moderately to severely reduced, 15 to 29 severely reduced, and below 15 it is called kidney failure. The lower the eGFR and the more protein in the urine, the greater the risk of further decline and of cardiovascular disease. According to the NHG, in people over 65 an eGFR between 45 and 60 without protein in the urine gives only a slightly increased risk. A single low value can also be temporary: due to dehydration, illness, heavy exercise, creatine supplements or medicines that raise creatinine. Symptoms only develop with severely reduced kidney function.

After an abnormal result

With a first eGFR below 60, the GP repeats the test within 3 months, or within a few days to a week with an unexpectedly strongly reduced value, and has the albumin-creatinine ratio in the urine measured. If the abnormality is still present after 3 months, the GP diagnoses chronic kidney damage, determines the risk stage and starts monitoring blood pressure, glucose and cholesterol. With an eGFR below 30, a lot of protein in the urine or a rapid decline, referral to an internist-nephrologist follows.

Reliability

How reliable is the test?

The eGFR is an estimate with a margin of error of roughly 10 to 20 percent, and the formula assumes an average muscle mass. In people with a lot of muscle (strength athletes) the eGFR underestimates kidney function, in people with little muscle it overestimates it. According to the Dutch GP guideline (NHG) and the Dutch medical specialists' guideline (FMS), an abnormal eGFR is always confirmed with a repeat measurement and supplemented with a urine test for albumin; if in doubt, the laboratory can also estimate kidney function based on cystatin C, which does not depend on muscle mass.

What can affect the result?

A lot of or little muscle mass, creatine supplements, amputation, malnutrition and pregnancy make the estimate unreliable; the formula does not apply to children.
Dehydration, heavy exercise, a meat meal and medicines such as trimethoprim, cimetidine and NSAIDs lower the eGFR temporarily.
The eGFR says nothing about protein loss through the kidneys; that requires a urine test (albumin-creatinine ratio), even with a normal eGFR.
Chronic kidney damage can only be diagnosed if the abnormality has been present for at least 3 months; a single result is not a diagnosis.

Who it is for

Who is the test useful for?

Useful for

Useful with diabetes, high blood pressure, cardiovascular disease, kidney disease in the family and with medicines that are excreted by the kidneys or put a strain on them; also in strength athletes and creatine users, with the caveat that the estimate is less reliable in them. In healthy adults without risk factors, the chance of reduced kidney function is small, especially under the age of 50; a slightly low value is then often temporary or fits the person's age. For them, the eGFR is mainly useful if the value needs to be known for another reason, such as when a medicine is prescribed.

How common is it?

Chronic kidney damage affects about 1 in 10 adults in the Netherlands. Under the age of 50 it is rare; over 65, an estimated more than 1 in 5 people have an eGFR below 60. In about 5 in 100 Dutch people, chronic kidney damage is known to the GP; so most people with reduced kidney function do not know it.

NHG guideline on chronic kidney damage; NIVEL primary care registrations (2021)

Drawbacks and risks

In strength athletes and creatine users, the eGFR is consistently too low; this can wrongly look like kidney damage.
A slightly low eGFR at an older age often fits the person's age; the label of kidney damage can then cause unnecessary worry.

Get tested

eGFR: test panels

eGFR is part of these test panels. You order online and have your blood drawn at a collection point or collect the sample at home.

Fingerstick
Creatinine
Measure your kidney function at home with creatinine finger prick including eGFR and CKD-EPI calculation.
€ 17,00
Blood draw
Creatinine
Measure your kidney function with creatinine including eGFR and CKD-EPI calculation.
€ 17,00
Blood draw
Hormones Male
Total testosterone, free testosterone, SHBG, creatinine, and eGFR. For men with hypogonadism, low libido, or during strength training.
€ 125,00
Blood draw
Endurance Sports
Complete blood count, iron status (ferritin, transferrin), kidney function, liver function, testosterone, and hs-CRP. For athletes and endurance sport participants.
€ 203,00
Blood draw
General Blood Test (Basic)
Hemoglobin, MCV, TSH, fT4, eGFR, creatinine, ALT, AST, sodium, and potassium. General health check of kidney, liver, and thyroid.
€ 125,00
Blood draw
Comprehensive Blood Test
Comprehensive blood test covering blood count, thyroid, kidney and liver function, glucose, inflammation markers and cholesterol.
€ 215,00
Blood draw
Heart Complete Test
Lipid profile, kidney function, glucose, HbA1c, and NT-proBNP cardiac marker. Comprehensive cardiovascular health check.
€ 105,00
Blood draw
Cardio Profile Extensive
Complete lipids, Lipoprotein(a), Apolipoprotein B/A1, kidney function and blood sugar. Advanced cardiovascular risk analysis.
€ 165,00
Blood draw
Kidney Function
Creatinine, eGFR, sodium, and potassium. Checks kidney health and electrolyte balance for diabetes, high blood pressure, or medication use.
€ 75,00

How reliable is the test?

eGFR

eGFR: what is measured?

What can it detect?

What does the result mean?

eGFR too high

eGFR too low

After an abnormal result

How reliable is the test?

What can affect the result?

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

eGFR: test panels

Creatinine

Creatinine

Hormones Male

Endurance Sports

General Blood Test (Basic)

Comprehensive Blood Test

Heart Complete Test

Cardio Profile Extensive

Kidney Function

Sources

Other tests: Kidneys and electrolytes

eGFR

eGFR: what is measured?

What can it detect?

What does the result mean?

eGFR too high

eGFR too low

After an abnormal result

How reliable is the test?

What can affect the result?

Who is the test useful for?

Useful for

How common is it?

Drawbacks and risks

eGFR: test panels

Creatinine

Creatinine

Hormones Male

Endurance Sports

General Blood Test (Basic)

Comprehensive Blood Test

Heart Complete Test

Cardio Profile Extensive

Kidney Function

Sources

Other tests: Kidneys and electrolytes