An eGFR result is an estimate of kidney filtration, not a diagnosis by itself. This practical guide explains eGFR stages, shows how to compare results over time, highlights factors that can distort interpretation, and provides questions to take to a clinician before making decisions about medicines or follow-up.
Overview
Estimated glomerular filtration rate, or eGFR, is calculated mainly from a blood creatinine result and other routinely collected information. It estimates how well the kidneys filter waste from the blood. Laboratories usually report it in milliliters per minute per 1.73 square meters of body-surface area, written as mL/min/1.73 m².
There is no single “normal” eGFR that applies to every person. Results tend to vary with age and body composition, and a single value can be affected by hydration, recent illness, diet, exercise, and medications. A lower result deserves context rather than an immediate conclusion. Kidney function is generally assessed by looking at repeat eGFR results together with urine testing, blood pressure, medical history, symptoms, and medication use.
Chronic kidney disease, or CKD, is not diagnosed from one low eGFR alone. In general, CKD involves a kidney abnormality that persists for more than three months. An eGFR below 60 that remains present over that period can support a CKD diagnosis. An eGFR of 60 or higher may still be clinically important when there are other persistent signs of kidney damage, such as albumin in the urine or structural abnormalities.
eGFR stages at a glance
| Category | eGFR range | What it generally means |
|---|---|---|
| G1 | 90 or higher | Usually preserved filtration; CKD requires another marker of kidney damage or an abnormal finding. |
| G2 | 60–89 | Mildly reduced estimate; CKD requires another marker of kidney damage or an abnormal finding. |
| G3a | 45–59 | Mild to moderately reduced filtration. |
| G3b | 30–44 | Moderately to severely reduced filtration. |
| G4 | 15–29 | Severely reduced filtration; specialist assessment may be appropriate. |
| G5 | Below 15 | Kidney failure range; requires prompt clinical assessment and individualized planning. |
These categories describe filtration, not the whole risk picture. Urine albumin is commonly reported as the urine albumin-to-creatinine ratio, or ACR. Broadly, A1 is below 30 mg/g, A2 is 30–300 mg/g, and A3 is above 300 mg/g. A higher or persistent ACR can increase concern even when eGFR is relatively preserved.
Checklist by scenario
If this is your first abnormal result
- Write down the eGFR, creatinine, date, and laboratory reference information.
- Ask whether the result could reflect dehydration, a recent infection, vomiting, diarrhea, or another temporary illness.
- Check whether a urine ACR or routine urinalysis was performed.
- Ask when the blood test should be repeated and whether any additional testing is needed.
- Do not stop a prescribed medicine or change its dose without speaking with the prescriber.
If you are comparing repeat results
- Compare results from the same laboratory when possible, because methods and reporting practices can differ.
- Record the dates rather than focusing only on the highest or lowest number.
- Look for a persistent pattern, a gradual change, or a sudden change associated with illness or a medication change.
- Review creatinine, potassium, urine ACR, blood pressure, and relevant symptoms alongside eGFR.
- Ask whether the change is large enough or persistent enough to require earlier follow-up.
If eGFR is low or falling
- Ask what may be contributing, including high blood pressure, diabetes, urinary obstruction, kidney disease, or medication effects.
- Request a medication and supplement review, including over-the-counter pain relievers and herbal products.
- Ask whether cystatin C testing or another method could clarify the estimate in your situation.
- Discuss kidney-protective care, blood pressure goals, urine albumin, and the appropriate follow-up interval.
- Ask whether referral to a kidney specialist is indicated based on the full pattern, not eGFR alone.
What to double-check
eGFR is an estimate based on a mathematical equation. It may be less reliable when creatinine production is unusually high or low, such as with very low muscle mass, amputation, severe malnutrition, unusually muscular build, or some neuromuscular conditions. Pregnancy, rapidly changing kidney function, and acute illness can also make a routine eGFR harder to interpret. Tell the clinician about these circumstances rather than trying to adjust the number yourself.
Recent strenuous exercise, a large meat intake, creatine supplements, and dehydration may influence creatinine and therefore the calculated eGFR. Some medicines can change creatinine handling without causing the same degree of change in filtration, while others can contribute to kidney injury. A clinician or pharmacist should review the complete medication list before any treatment is altered.
Ask whether the laboratory used the current creatinine-based equation and whether cystatin C could add useful information. Cystatin C is another blood-based marker that may help when creatinine-based interpretation is uncertain. Neither test should be treated as a stand-alone diagnosis.
Common mistakes
- Calling one result CKD: chronic disease usually requires persistence or other evidence of kidney damage.
- Treating a higher number as proof of healthy kidneys: urine albumin, blood pressure, imaging, and medical history still matter.
- Comparing unrelated laboratory results: dates, laboratories, equations, and health conditions at the time of testing affect comparisons.
- Changing medicines independently: some drugs require dose adjustments at lower eGFR, but abrupt changes can also be harmful.
- Ignoring urine testing: albumin and blood in the urine can provide important information that eGFR does not show.
- Assuming a small fluctuation is a definite decline: clinicians interpret the direction and size of change in context.
Seek urgent medical advice for severe shortness of breath, chest pain, confusion, markedly reduced urine, severe swelling, or symptoms of serious illness. These symptoms need assessment regardless of the eGFR value.
When to revisit
Return to this checklist whenever a new kidney blood test is available, after a hospital stay or significant illness, or when a clinician starts, stops, or changes a medicine that may affect kidney function. Revisit it before imaging tests or procedures if you have been told your kidney function is reduced, because the care team may need current results and a medication review.
At each review, keep a simple record containing the test date, eGFR, creatinine, urine ACR, blood pressure, symptoms, and medication changes. Bring the record to appointments and ask three practical questions: Is this result persistent? What is the likely explanation for the trend? and What should be checked next, and when? If results are declining, urine albumin is elevated, or the cause is unclear, ask whether earlier follow-up or kidney-specialist input is appropriate. This approach turns an isolated lab number into a safer, more useful picture of kidney health.
