eGFR stands for estimated glomerular filtration rate, and it measures how well your kidneys are filtering waste from your blood. It appears on routine blood work as a number, typically ranging from 0 to 120 or higher, with a normal result being 90 or above. If you’ve spotted this value on a lab report and aren’t sure what it means, the short answer is: it’s the single most important number for gauging your kidney function.
What eGFR Actually Measures
Your kidneys contain roughly one million tiny filtering units called glomeruli. Every minute, these filters process about half a cup of blood, pulling out waste products and excess fluid that leave your body as urine. The glomerular filtration rate is the speed at which this filtering happens, measured in milliliters per minute.
Directly measuring that filtration rate is complex and impractical for routine checkups, so labs estimate it instead. They measure a waste product called creatinine in your blood. Creatinine is produced at a fairly steady rate by your muscles, and healthy kidneys clear it efficiently. When kidney function declines, creatinine builds up. The lab plugs your creatinine level into a formula along with your age, sex, and sometimes your body size to calculate the eGFR. The “e” simply means estimated.
A higher eGFR means your kidneys are filtering well. A lower number means they’re struggling. The result is standardized so it reflects what your filtration rate would be if you had average-sized kidneys, making it comparable across different people.
What the Numbers Mean
An eGFR of 90 or above is considered normal, as long as there are no other signs of kidney damage like protein in the urine. Many healthy adults have values between 90 and 120. Values above 120 can occur and are not typically a concern.
Below 90, doctors start paying closer attention. Kidney disease is classified into five stages based on eGFR:
- Stage 1 (eGFR 90+): Normal filtration, but other markers like protein in the urine suggest early kidney damage.
- Stage 2 (eGFR 60–89): Mildly reduced function. Many people at this stage feel completely fine and may never progress further.
- Stage 3a (eGFR 45–59): Mild to moderate loss of function. This is often where monitoring becomes more frequent.
- Stage 3b (eGFR 30–44): Moderate to severe reduction. Waste products may start building up in the blood.
- Stage 4 (eGFR 15–29): Severe loss of function. Symptoms like fatigue, swelling, and changes in urination become more common.
- Stage 5 (eGFR below 15): Kidney failure. The kidneys can no longer sustain life without dialysis or a transplant.
A single eGFR reading below 90 doesn’t automatically mean you have kidney disease. Labs have margins of error, and your filtration rate naturally fluctuates day to day. Doctors typically want to see a persistently low result, confirmed on repeat testing over at least three months, before diagnosing chronic kidney disease.
Why eGFR Appears on Routine Blood Work
Chronic kidney disease affects roughly 1 in 7 adults in the United States, and the vast majority of people in early stages have no symptoms at all. Because kidney damage is largely irreversible but its progression can be slowed, catching it early matters. That’s why eGFR is automatically calculated whenever a basic or comprehensive metabolic panel includes creatinine, which is most routine blood draws.
You’re especially likely to see eGFR tracked if you have diabetes, high blood pressure, heart disease, or a family history of kidney problems. These are the leading risk factors for kidney disease, and regular eGFR monitoring helps catch declining function before it becomes severe.
Factors That Can Affect Your Result
Because eGFR is calculated from creatinine, anything that changes your creatinine level can shift the estimate. People with significantly more muscle mass tend to produce more creatinine, which can make their eGFR appear lower than their actual kidney function. The reverse is true for people with very low muscle mass, including older adults or those with chronic illness, where eGFR may look deceptively normal despite reduced kidney function.
Dehydration, intense exercise in the 24 hours before your blood draw, and high-protein meals can all temporarily raise creatinine and push eGFR down. Certain medications, including some common anti-inflammatories, can also affect the result without reflecting true kidney damage.
The formula used to calculate eGFR has been updated over the years. Older equations factored in race, but the most widely adopted current formula, called CKD-EPI 2021, removed race as a variable. If you’re comparing results across several years of lab work, small shifts may partly reflect a change in the equation your lab uses rather than a real change in kidney function.
eGFR vs. Creatinine: Why Both Appear
You’ll often see both creatinine and eGFR on the same lab report, and it’s natural to wonder why both are listed. Creatinine alone is hard to interpret because what counts as “normal” varies by age, sex, and body composition. A creatinine level of 1.2 mg/dL might be perfectly fine for a muscular 30-year-old man but could signal reduced kidney function in a 75-year-old woman. eGFR adjusts for these differences, making it a more reliable snapshot of how your kidneys are actually performing.
In certain situations, doctors may also order a separate urine test called albumin-to-creatinine ratio to check whether your kidneys are leaking protein. Healthy kidneys keep protein in the blood, so finding it in the urine alongside a low eGFR strengthens the case that kidney damage is present. The two tests together give a much fuller picture than either one alone.
What a Low eGFR Means for You
If your eGFR comes back between 60 and 89 with no protein in your urine and no other risk factors, it may simply reflect normal variation or a temporary dip. Your doctor will likely recheck it on a future blood draw and compare the trend.
If your eGFR is consistently below 60, the focus shifts to protecting the kidney function you still have. The most effective strategies target the conditions that drive kidney damage in the first place: keeping blood pressure well controlled, managing blood sugar if you have diabetes, staying hydrated, and avoiding medications that are hard on the kidneys, particularly over-the-counter anti-inflammatory painkillers used frequently. Newer medications originally developed for diabetes have shown significant kidney-protective effects even in people without diabetes, and these are now increasingly prescribed for chronic kidney disease specifically.
Dietary changes may also come into play at lower eGFR levels. Reducing sodium intake helps with blood pressure and fluid retention. At more advanced stages, you may be advised to limit potassium, phosphorus, or protein, because damaged kidneys struggle to process these efficiently. The specifics depend on your lab values and stage.
How Fast Can eGFR Change?
In healthy adults, eGFR naturally declines by about 1 mL/min per year after age 30 as part of normal aging. A faster decline, generally considered more than 3 to 5 mL/min per year, raises concern and prompts closer investigation into what’s driving the loss.
Acute illnesses, severe dehydration, or reactions to medication can cause eGFR to drop sharply over days or weeks. This is called acute kidney injury, and it’s often reversible once the underlying cause is treated. Chronic kidney disease, by contrast, develops gradually over months or years and is generally not reversible, though its progression can be significantly slowed with the right management. Tracking your eGFR over time, rather than fixating on any single number, gives the most meaningful picture of your kidney health.