A healthy GFR (glomerular filtration rate) is generally 90 mL/min or above, though the number naturally decreases with age. For a 20-year-old, an average GFR of 116 is typical, while a healthy 70-year-old might sit around 75 without any kidney disease. Understanding where your number falls, and whether it’s appropriate for your age, matters more than hitting a single universal target.
What GFR Actually Measures
GFR tells you how efficiently your kidneys filter blood. Specifically, it measures how many milliliters of blood your kidneys clean per minute. The higher the number, the better your kidneys are working. When you get blood work, your lab report will show an “eGFR,” which is an estimate based on a blood marker called creatinine along with your age and sex. The current standard formula, adopted in 2021, no longer includes a racial adjustment, a change recommended by the National Kidney Foundation and American Society of Nephrology to reduce health disparities.
Average GFR by Age
Your kidneys lose a small amount of filtering capacity every year, even in perfect health. Blood flow to the kidneys drops by roughly 10% per decade starting around age 30. In healthy adults without high blood pressure, the typical decline is between 0.4 and 1.1 points per year. That pace tends to accelerate slightly after age 50.
Here’s what average eGFR looks like across age groups:
- 20 to 29: 116
- 30 to 39: 107
- 40 to 49: 99
- 50 to 59: 93
- 60 to 69: 85
- 70 and older: 75
This means a GFR of 78 in a 72-year-old is perfectly normal, while that same number in a 35-year-old would be a red flag. Context matters as much as the number itself.
GFR Stages of Kidney Disease
Kidney function is classified into stages based on GFR, which helps doctors gauge how much filtering ability remains:
- Stage 1 (GFR 90 or above): Normal or high function. You can still be in this category and have kidney disease if other signs of damage are present, like protein in your urine.
- Stage 2 (GFR 60 to 89): Mildly decreased. Many older adults fall here naturally. This only counts as chronic kidney disease if there’s also evidence of kidney damage lasting at least three months.
- Stage 3a (GFR 45 to 59): Mild to moderate decrease.
- Stage 3b (GFR 30 to 44): Moderate to severe decrease.
- Stage 4 (GFR 15 to 29): Severe decrease.
- Stage 5 (GFR below 15): Kidney failure.
One important detail: a GFR below 60 alone is enough to qualify as chronic kidney disease. But between 60 and 89, you need an additional marker of kidney damage, such as elevated protein in your urine (an albumin-to-creatinine ratio of 30 mg/g or higher), abnormalities on imaging, or blood in the urine. That marker also needs to persist for at least three months before a CKD diagnosis applies.
When Symptoms Actually Appear
One of the tricky things about kidney disease is that you can lose a significant amount of function before feeling anything. Stages 1 and 2 are almost always silent. Most people first notice symptoms in Stage 3, when GFR drops between 30 and 59. At that point, waste products start building up in the blood and you might feel unusually tired or weak, or notice swelling in your hands and feet.
By Stage 4 (GFR 15 to 29), symptoms become more pronounced. Swelling, back pain, and changes in urination are common. At Stage 5, the kidneys can no longer keep up with the body’s needs, and waste buildup can make you seriously ill. This is the stage where dialysis or transplant becomes necessary.
Why Your eGFR Might Be Inaccurate
The standard eGFR test estimates kidney function based on creatinine, a waste product generated by your muscles. That works well for most people, but it can be misleading if your muscle mass is unusually high or low. Bodybuilders, for instance, produce more creatinine and may get a falsely low eGFR. On the other hand, frail older adults, people with amputations, those with muscle-wasting conditions, or anyone eating a very low-meat or vegetarian diet may produce less creatinine, which can make their kidneys look healthier than they are.
Creatinine-based eGFR also tends to overestimate kidney function in older people, potentially masking early kidney disease. If your doctor suspects the standard test isn’t telling the full story, they may order a cystatin C test. Cystatin C is a protein that isn’t affected by muscle mass, making it a more reliable marker in people at the extremes of body composition. The most accurate estimates come from combining both creatinine and cystatin C in a single equation, which performs particularly well in older adults and when GFR is in the 45 to 59 range where staging decisions are made.
Certain medications and conditions can also throw off results. Thyroid problems, steroid use, and significant inflammation can affect cystatin C levels, while some common drugs interfere with creatinine measurement. A single abnormal result isn’t necessarily cause for alarm, which is partly why doctors look for patterns over three months before diagnosing chronic kidney disease.
Protecting Your GFR Over Time
Blood pressure is the single most important modifiable factor for preserving kidney function. High blood pressure damages the tiny blood vessels in the kidneys, accelerating the natural decline. In people without hypertension, the yearly GFR loss stays in that 0.4 to 1.1 range. With uncontrolled hypertension, it can more than triple, reaching up to 3.6 points per year.
Research on lifestyle interventions in people with existing kidney disease shows that exercise appears to offer the greatest improvements in eGFR, while dietary changes have the strongest effect on reducing protein in the urine (a key marker of kidney damage) and lowering blood pressure. A diet rich in fruits and vegetables may also help by reducing acid buildup in the blood, which has been shown to preserve GFR in people with Stage 3 kidney disease. Sodium restriction is another commonly studied approach, though its direct effect on GFR is harder to isolate from its benefit on blood pressure.
Staying well-hydrated, maintaining a healthy weight, and managing blood sugar if you have diabetes are all protective. These won’t stop the natural age-related decline, but they can keep it from accelerating into disease territory.