Guides · Lab results

What your eGFR blood test means: kidney function stages

eGFR (estimated glomerular filtration rate) estimates how much blood your kidneys filter each minute, worked out from your blood creatinine, age and sex. An eGFR of 90 or higher is in the normal range, 60 to 89 can mean early kidney disease, and below 60 for three months or more points to chronic kidney disease.

eGFR falls slowly with age even in healthy people, and anything that changes creatinine, such as muscle mass, a big meat meal or creatine supplements, changes eGFR too. One low reading is a reason to recheck, not a diagnosis.

Updated · Facts checked against the sources listed below

Gabriel Optimal Range StandardTypical lab reference ranges vary by lab. Your lab's own flag decides what is abnormal; Gabriel's optimal range is a target to discuss with your clinician.
MarkerGabriel optimalTypical lab rangeFunctional range
eGFR90 to 160 mL/min/1.7360 or higher90 or higher

What eGFR measures

Your kidneys filter waste out of your blood. Measuring that filtering directly is slow and costly, so labs estimate it. They take your creatinine, a waste product from normal muscle use, and plug it into a formula with your age and sex. The result is reported in mL/min/1.73m².

Some labs also use cystatin C, a blood protein that muscle size and diet affect less. An eGFR based on both creatinine and cystatin C is more accurate than either alone. See the GFR lab guide.

eGFR and kidney disease stages

Stages from the National Kidney Foundation. Each needs results that last 3 months or more; one test is not enough.
StageeGFRWhat it means
G190 or higherNormal filtering. Counts as kidney disease only with other signs of damage, such as albumin in the urine
G260 to 89Mildly lower. Counts as kidney disease only with signs of damage
G3a45 to 59Mild to moderate loss of function
G3b30 to 44Moderate to severe loss of function
G415 to 29Severe loss of function
G5Below 15Kidney failure

eGFR is only half the picture. A urine test called the urine albumin-to-creatinine ratio (UACR) shows whether protein is leaking through the kidneys. Above 30 mg/g can mean kidney damage, even with a normal eGFR.

Normal eGFR by age

eGFR drifts down with age, even without kidney disease. Average values from the National Kidney Foundation:

Averages, not targets. Your trend over time matters more than one result.
AgeAverage eGFR
20 to 29116
30 to 39107
40 to 4999
50 to 5993
60 to 6985
70 and older75

Gabriel's optimal range is 90 or higher, which many healthy older adults won't reach. A steady result in the 60s or 70s at an older age is read differently from a fall from 100 to 70 in a year.

What can make eGFR look lower or higher

Since most eGFR results come from creatinine, things that raise creatinine make eGFR look lower than your real kidney function:

  • High muscle mass, as in very muscular people or bodybuilders.
  • Creatine supplements.
  • A large amount of cooked meat before the test.
  • Recent hard exercise.
  • Some medicines, such as trimethoprim, cimetidine and some HIV medicines, which raise creatinine without harming the kidneys.
  • Dehydration.

The opposite can make eGFR look higher than it really is: low muscle mass, a vegetarian or vegan diet, pregnancy, an amputation or a muscle-wasting disease, and severe liver disease.

What to do with a low eGFR

  1. Recheck in about 3 months, or sooner if your clinician advises. Avoid hard exercise, a big meat meal and creatine before the retest, and tell your clinician if you take creatine.
  2. Ask for a urine albumin test (UACR) and, if creatinine might be misleading, a cystatin C test.
  3. Bring past results. The trend tells more than one number.
  4. Review medicines and supplements with your clinician. Don't stop any prescribed medicine on your own.
  5. Ask about blood pressure and blood sugar. Diabetes and high blood pressure are major risk factors for kidney disease.

Get prompt care if a low or falling eGFR comes with much less urine than usual, swelling in your legs, ankles or face, shortness of breath, confusion, or nausea and vomiting.

Common questions

What is a normal eGFR?

In adults, 90 or higher is in the normal range, and most labs flag results below 60. eGFR falls with age, so an average 70-year-old has an eGFR around 75. Gabriel's optimal range is 90 to 160.

Is an eGFR of 60 bad?

An eGFR of 60 to 89 can be early kidney disease if there are other signs of damage, but it is also common in healthy older adults. Below 60 for three months or more points to chronic kidney disease.

Can creatine supplements lower eGFR?

They can make eGFR look lower, because creatine raises blood creatinine. That doesn't by itself mean kidney damage. Tell your clinician you take it, and ask whether a cystatin C test makes sense.

Can dehydration lower eGFR?

Yes. Dehydration can raise creatinine and lower eGFR for a while. A recheck when you are well hydrated gives a truer picture.

Can eGFR go back up?

A low reading caused by dehydration, exercise, a meat meal or a supplement often returns to baseline on a recheck. With true chronic kidney disease, the goal is to keep eGFR from falling further.

Sources

  1. Estimated Glomerular Filtration Rate (eGFR) National Kidney Foundation
  2. CKD Stages G1 to G5 National Kidney Foundation
  3. Creatinine National Kidney Foundation
  4. Glomerular Filtration Rate (GFR) Test MedlinePlus, U.S. National Library of Medicine
  5. Chronic Kidney Disease Tests and Diagnosis National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

This guide is general information, not medical advice. It does not replace a visit with a licensed clinician. Gabriel membership is not health insurance.