eGFR Test
Also known as: Estimated Glomerular Filtration Rate, GFR, Glomerular Filtration Rate
What is eGFR?
eGFR (estimated Glomerular Filtration Rate) estimates how well your kidneys filter waste from your blood. It is the best overall measure of kidney function.[MedlinePlus (NIH)]
What This Test Measures
eGFR is calculated from creatinine levels, age, sex, and race. It estimates the volume of blood filtered by the kidneys per minute (mL/min/1.73m²).[Cleveland Clinic]
Why It's Important
eGFR is used to diagnose and stage chronic kidney disease (CKD) and monitor kidney function over time.[MedlinePlus (NIH)]
Early detection of declining kidney function allows treatment to slow progression.[Cleveland Clinic]
Who Should Get This Test?
eGFR should be routinely monitored in people with risk factors for kidney disease. It is included in most comprehensive metabolic panels.
Risk Factors
- Diabetes (leading cause of kidney failure)
- High blood pressure (second leading cause)
- Family history of kidney disease
- Age over 60
- Cardiovascular disease (heart disease, stroke)
- Obesity (BMI > 30)
- African American, Hispanic, Native American, Asian American, or Pacific Islander ethnicity
- History of acute kidney injury
- Long-term use of NSAIDs (ibuprofen, naproxen)
- Kidney stones or urinary tract abnormalities
- Autoimmune diseases (lupus, rheumatoid arthritis)
- Current smoker
Screening Schedule
Annual testing recommended for people with diabetes, hypertension, or other risk factors. More frequent monitoring (every 3-6 months) once CKD is diagnosed.
Why Your Doctor May Order This Test
Your doctor orders an eGFR test because it is the best single measure of overall kidney function. Unlike creatinine alone, eGFR accounts for age, sex, and other factors to give a more accurate picture of how well your kidneys are filtering blood.
- To screen for chronic kidney disease (CKD), especially if you have diabetes, hypertension, or family history
- To diagnose kidney disease and determine its stage (1-5)
- To monitor kidney function in people with known CKD
- Before prescribing medications that are cleared by the kidneys (dosage adjustments may be needed)
- To monitor kidney function when taking medications that can affect the kidneys (NSAIDs, certain antibiotics, contrast dye)
- As part of a comprehensive metabolic panel during routine health checkups
- To assess kidney involvement in systemic diseases (lupus, diabetes, hypertension)
- To determine if you are a candidate for kidney donation
- To monitor kidney function after a kidney transplant
How to Prepare for This Test
Fasting Requirements
No fasting required. You can eat and drink normally before this test.
Best Time for Testing
The test can be done at any time of day. For consistent tracking over time, try to test at approximately the same time of day.
Things to Avoid Before Testing
- ✗Heavy meat consumption the day before (temporarily elevates creatinine)
- ✗Creatine supplements (directly affects creatinine levels used to calculate eGFR)
- ✗Strenuous exercise 24 hours before the test (can temporarily raise creatinine)
- ✗Excessive protein intake the day before testing
eGFR is calculated from your blood creatinine level along with your age and sex. Recent guidelines have moved away from using race in the calculation. Factors like extreme muscle mass, malnutrition, or limb amputation can affect accuracy. For more precise kidney function assessment, your doctor may order a cystatin C-based eGFR or a 24-hour urine collection.
Source: Cleveland ClinicWhat Happens During the Test
eGFR is calculated from your blood creatinine level, which is measured from a standard blood draw. A healthcare provider draws blood from a vein in your arm. The lab measures creatinine and calculates eGFR using a formula that accounts for age, sex, and body size.
Duration
Less than 5 minutes for the blood draw. Results typically available within 1-2 days.
Discomfort Level
Brief sting when the needle is inserted. Mild discomfort is normal.
Risks & Side Effects
The blood test for eGFR is very safe with minimal risks.
- •Slight pain or bruising at the needle site
- •Lightheadedness (rare)
- •Very rarely, infection at the puncture site
Normal Range
Normal: 90 or above. Mildly decreased: 60-89. Moderately decreased: 45-59. Severely decreased: 15-44. Kidney failure: Below 15.
Note: eGFR naturally declines with age. Values below 60 for 3+ months indicate CKD.
Source: MedlinePlus (NIH)High Values
Very high eGFR (above 120) may indicate hyperfiltration, which can occur early in diabetes. Generally, higher is better.[Cleveland Clinic]
Low Values
Low eGFR indicates reduced kidney function. CKD is diagnosed when eGFR is below 60 for 3 or more months. Causes include diabetes, high blood pressure, and glomerulonephritis.[MedlinePlus (NIH)]
What Causes High eGFR?
Very high eGFR (above 120 mL/min/1.73m²) is uncommon and usually indicates hyperfiltration. While higher eGFR is generally better, abnormally high values may warrant attention.
- Hyperfiltration in early diabetes (before kidney damage becomes apparent)
- Pregnancy (kidney filtration naturally increases by 50%)
- High protein diet temporarily increasing filtration
- Very low muscle mass (may cause falsely elevated eGFR)
- Early stages of certain kidney diseases
- After eating a large protein meal (temporary increase)
What Causes Low eGFR?
Low eGFR indicates reduced kidney filtering capacity. Chronic kidney disease is diagnosed when eGFR stays below 60 for 3 or more months. The lower the eGFR, the more severe the kidney impairment.
- Diabetic nephropathy (kidney damage from diabetes)—the leading cause of kidney failure
- Hypertensive nephropathy (kidney damage from high blood pressure)—the second leading cause
- Glomerulonephritis (inflammation of kidney filtering units)
- Polycystic kidney disease (inherited condition causing cysts)
- Chronic use of NSAIDs (ibuprofen, naproxen) causing analgesic nephropathy
- Recurrent kidney infections (pyelonephritis)
- Kidney stones causing obstruction
- Autoimmune diseases (lupus nephritis)
- Heart failure (reduced blood flow to kidneys)
- Dehydration (temporary decrease)
- Age-related decline (eGFR naturally decreases about 1 mL/min/year after age 40)
- Medications: certain antibiotics, chemotherapy, contrast dye
- Previous acute kidney injury
How to Improve Your eGFR Levels
While kidney damage cannot always be reversed, you can slow or halt CKD progression significantly with proper management. The key is early detection and aggressive treatment of underlying causes.
- 1.Control blood pressure: Target below 130/80 mmHg for most CKD patients. ACE inhibitors or ARBs are preferred as they protect kidney function
- 2.Manage blood sugar: If diabetic, keep A1C below 7% (or your doctor's target). Good glucose control dramatically slows kidney damage progression
- 3.Reduce sodium intake: Limit to under 2,300 mg/day (ideally under 1,500 mg). Excess sodium raises blood pressure and stresses kidneys
- 4.Moderate protein intake: In advanced CKD (stages 3-5), excessive protein may accelerate decline. Consult a renal dietitian
- 5.Stay hydrated: Drink adequate water, but don't overhydrate. Follow your doctor's fluid recommendations
- 6.Avoid NSAIDs: Ibuprofen, naproxen, and similar drugs can worsen kidney function. Use acetaminophen for pain when possible
- 7.Stop smoking: Smoking accelerates kidney disease progression and increases cardiovascular risk
- 8.Exercise regularly: Moderate activity improves blood pressure, blood sugar, and overall health
- 9.Maintain healthy weight: Obesity increases CKD risk and progression
- 10.Avoid contrast dye if possible: If imaging with contrast is necessary, ensure proper hydration protocols
- 11.Review all medications with your doctor: Some need dose adjustments with reduced kidney function
How Often Should You Get Tested?
For healthy adults: Every 1-3 years as part of routine checkups. With diabetes or hypertension: At least annually. With CKD stage 1-2 (eGFR 60-90): Every 12 months. CKD stage 3 (eGFR 30-59): Every 3-6 months. CKD stage 4 (eGFR 15-29): Every 1-3 months. CKD stage 5 (eGFR <15): As directed by nephrologist. After starting medications affecting kidneys: Recheck in 1-2 weeks.
Source: MedlinePlus (NIH)Test Limitations & Accuracy
eGFR is an estimate and may not be accurate in certain situations. Your doctor may use additional tests when precision is important.
- ⚠Extreme muscle mass (bodybuilders may have falsely low eGFR)
- ⚠Very low muscle mass, malnutrition, or amputations (falsely high eGFR)
- ⚠Acute changes in kidney function (eGFR reflects steady-state function)
- ⚠Creatine supplements (directly affects creatinine levels)
- ⚠High protein diet (temporarily elevates creatinine)
- ⚠Certain medications affecting creatinine secretion
- ⚠Pregnancy (kidney function increases normally)
- ⚠Children (different equations needed)
- ⚠Very elderly (may overestimate function)
Alternative & Complementary Tests
For more accurate kidney function assessment or when creatinine-based eGFR may be inaccurate, doctors may use:
Alternative marker not affected by muscle mass. Often combined with creatinine for more accurate eGFR.
Gold standard for GFR measurement. Requires 24-hour urine collection.
Used alongside creatinine. BUN/Creatinine ratio helps identify cause of kidney dysfunction.
Detects early kidney damage even when eGFR is normal. Important in diabetes.
Imaging to assess kidney size, structure, and rule out obstruction.
Definitive diagnosis of underlying kidney disease when cause is unclear.
Related Tests
These tests are often ordered together or provide complementary information:
Frequently Asked Questions
How can I improve my eGFR?
Protect kidney function by controlling blood pressure and blood sugar, reducing salt intake, staying hydrated, exercising, maintaining healthy weight, avoiding NSAIDs, and not smoking. Some kidney damage may be reversible if caught early.
Source: Cleveland ClinicWhat are the stages of chronic kidney disease?
Stage 1: eGFR 90+ with kidney damage. Stage 2: eGFR 60-89. Stage 3a: 45-59. Stage 3b: 30-44. Stage 4: 15-29. Stage 5: Below 15 (kidney failure).
Source: MedlinePlus (NIH)References
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Medical Disclaimer
This information is for educational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for interpretation of test results and medical decisions.
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