GFR (Glomerular Filtration Rate)
Blood test to measure kidney function by evaluating how well the kidneys filter waste from the blood.
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Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
What this test measures
The estimated glomerular filtration rate (eGFR) quantifies how efficiently the kidneys are filtering blood. The glomeruli are clusters of tiny blood vessels within the kidneys that serve as the primary filtration units, removing waste products and excess fluid from the bloodstream. eGFR estimates how much blood these structures clean per minute, providing a practical measure of overall kidney function.
The value is not measured directly but is calculated from a blood creatinine (or cystatin C) level using equations that account for age, sex, and other variables. This calculation produces a more accurate reflection of kidney function than creatinine alone, because creatinine levels are influenced by muscle mass and other factors that can make a raw number misleading. Healthcare providers use eGFR as the standard metric for staging chronic kidney disease, screening for early kidney impairment, and monitoring how kidney function changes over time in response to treatment or disease progression.
Who should consider this test
You might consider this test if you are experiencing any of the following:
- Individuals with diabetes or high blood pressure, as these conditions can damage kidney function over time
- Those with a family history of kidney disease or other risk factors for chronic kidney disease
- People taking medications that may affect kidney function or require dosage adjustments based on kidney health
- Individuals experiencing symptoms that could suggest kidney problems, such as frequent urination, swelling, or fatigue
- Those over age 60 who want to monitor normal age-related changes in kidney function
- People with heart disease, as kidney and cardiovascular health are closely connected
What to expect
Preparation
No fasting is typically required for this test. Individuals should maintain normal hydration levels and inform their healthcare provider of any medications being taken, as some may affect results. Avoiding excessive fluid intake or dehydration before the test helps ensure accurate results.
Sample Type
A small blood sample is drawn from a vein in the arm, similar to other routine blood tests. The sample is used to measure creatinine levels, which are then used in mathematical equations to calculate the estimated GFR.
Collection
The blood draw is performed quickly by a trained professional at the laboratory. The process takes only a few minutes and involves minimal discomfort. No special procedures or extended time at the lab is required.
Turnaround
Results are typically available within 1-2 business days. The eGFR is calculated automatically as part of the creatinine test processing, so no additional waiting time is needed for calculation.
Understanding your results
A normal eGFR for a healthy young adult is approximately 90 to 120 mL/min. An eGFR of 60 or above is generally considered within the functional range, while a sustained eGFR below 60 for three or more months is a key criterion for diagnosing chronic kidney disease. It is important to note that kidney filtration capacity naturally declines with age, even in people without kidney disease, so a modest reduction in an older adult may represent normal aging rather than pathology. Healthcare providers interpret eGFR alongside urine tests (such as albumin-to-creatinine ratio), blood pressure, diabetes status, and clinical symptoms to determine whether a reduced value reflects concerning kidney disease or age-appropriate function.
| Population | Reference Range | Notes |
|---|---|---|
| Healthy Adults (under 40) | 90-120+ mL/min/1.73 m² | Normal kidney function with optimal filtering capacity |
| Adults (40-70 years) | 80-120 mL/min/1.73 m² | May show mild age-related decline but typically remains in normal range |
| Adults (over 70 years) | 60-90 mL/min/1.73 m² | Age-related decline is expected; values 60-70 may be normal in this age group |
Reference ranges shown are general guidelines. Your lab report will include the specific reference range used by the laboratory that processed your sample, which is the authoritative range for interpreting your results.
What does a “Low” result mean?
A GFR of 60 or higher is in the normal range. A GFR below 60 may mean kidney disease. A GFR of 15 or lower may mean kidney failure. A healthcare provider may diagnose chronic kidney disease if eGFR stays below 60 for three months. Low eGFR values can be associated with various conditions including diabetes, high blood pressure, heart disease, or other factors that affect kidney function. The degree of reduction and persistence over time help healthcare providers determine if further evaluation or treatment may be needed. A GFR below 60 mL/min/1.73 m² may indicate a higher risk for CKD complications as well as cardiovascular disease.
What does a “High” result mean?
In general, the higher the GFR, the better. A GFR of 90 or higher is considered normal if individuals are healthy, unless they have other symptoms such as protein in their urine, which could still be a sign of kidney disease. However, very high eGFR values may occasionally indicate hyperfiltration, which can occur in early diabetes or other conditions where the kidneys are working harder than normal. This situation may require monitoring, as hyperfiltration can sometimes precede kidney damage over time. Most healthy individuals with high eGFR values simply have well-functioning kidneys.
Privacy & confidentiality
All test orders are authorized and results reviewed by an independent, board-certified physician who is not the patient's personal doctor. Your GFR test results are completely confidential and handled with the utmost privacy protection. Results are <u>not sent to your personal doctor</u> unless you specifically request it, ensuring you have complete control over your health information. The test results are <u>not added to your medical records</u> automatically and remain separate from your regular healthcare documentation. Additionally, these results will <u>not appear on insurance statements</u> or explanation of benefits (EOB), providing financial privacy for your testing. Your employer, insurance company, or other third parties cannot access these results without your explicit written consent. This confidential testing allows individuals to monitor their kidney health privately, whether for routine wellness screening or when there are concerns about kidney function. The privacy protection ensures you can make informed decisions about your health without concerns about potential impacts on insurance coverage or employment. No doctor visit is required to order this test, giving you direct access to important health information while maintaining complete confidentiality.
Frequently asked questions
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Last reviewed: April 2026
CPT Code: 82565
This test may not be available in: NY, NJ, RI
This page is for informational purposes only and does not constitute medical advice. Always consult with a healthcare provider regarding any health concerns. LevelPanel does not diagnose, treat, or prescribe.
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LevelPanel has no business or affiliate relationship with Quest or LabCorp. These links are provided as a public service.
Lab testing services linked from this site are not available to residents of Alaska, Arizona, or Hawaii, unless otherwise noted on the lab's own website.
This publication is not intended to solicit the purchase of laboratory testing from any individual consumer.
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