eGFR (Estimated Glomerular Filtration Rate)

What Is eGFR?

eGFR stands for estimated Glomerular Filtration Rate, and it is considered the best overall indicator of how well your kidneys are functioning. Unlike most lab values that are directly measured from your blood, eGFR is calculated using a formula. The lab takes your creatinine level and plugs it into an equation along with your age and sex to estimate how many milliliters of blood your kidneys can filter per minute. Think of it as a performance score for your kidneys — the higher the number, the better they are working.

What Does It Measure?

Your kidneys contain roughly one million tiny filtering units called glomeruli. Each one acts like a microscopic sieve, separating waste and excess fluid from the blood. The glomerular filtration rate is the total volume of blood these filters process per minute. Because it is difficult to measure this directly, laboratories estimate it using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation, which is the current gold standard. The 2021 CKD-EPI equation uses creatinine, age, and sex — without a race variable — to produce your eGFR number. A higher eGFR means more blood is being filtered and your kidneys are working efficiently. A lower eGFR means filtration has slowed down.

Normal Ranges

| Stage | eGFR Range | Unit | Interpretation | |---|---|---|---| | Normal or high | 90 or above | mL/min/1.73m2 | Healthy kidney function | | Mildly decreased | 60 – 89 | mL/min/1.73m2 | May be normal for age; monitor if other signs present | | Moderately decreased (Stage 3a) | 45 – 59 | mL/min/1.73m2 | Mild to moderate kidney disease | | Moderately decreased (Stage 3b) | 30 – 44 | mL/min/1.73m2 | Moderate to severe kidney disease | | Severely decreased (Stage 4) | 15 – 29 | mL/min/1.73m2 | Severe kidney disease | | Kidney failure (Stage 5) | Below 15 | mL/min/1.73m2 | Dialysis or transplant may be needed |

It is worth knowing that eGFR naturally declines with age. A healthy 25-year-old might have an eGFR of 120, while a healthy 75-year-old might sit at 75. An eGFR between 60 and 89 in an older adult, without protein in the urine or structural kidney abnormalities, may not indicate disease at all. Context matters enormously with this number.

What Does a High Level Mean?

Unlike most lab markers, a high eGFR is generally not a concern. It means your kidneys are filtering blood quickly. Values above 90 are considered normal. In some cases, a very high eGFR (above 120–130) could reflect hyperfiltration, where the kidneys are working harder than they should. This is sometimes seen in:

• Early diabetes: Before kidney damage becomes apparent, the kidneys may overcompensate and filter faster than normal.
• Pregnancy: Increased blood volume and cardiac output naturally raise GFR during pregnancy, which is expected and usually harmless.
• High-protein diets: Eating large amounts of protein can temporarily increase filtration rate.

Hyperfiltration usually does not cause symptoms. If your doctor suspects it in the setting of diabetes, they may monitor you more closely and check for early signs of kidney damage like microalbuminuria (small amounts of protein leaking into the urine).

What Does a Low Level Mean?

A low eGFR is the primary way kidney disease is diagnosed and staged. Possible causes include:

• Chronic kidney disease (CKD): The most common reason for a persistently low eGFR. CKD develops slowly, often over years, and is frequently linked to diabetes, high blood pressure, or both.
• Acute kidney injury (AKI): A sudden drop in eGFR can happen due to severe dehydration, blood loss, medication toxicity, or urinary tract obstruction.
• Glomerulonephritis: Inflammation of the kidney's filtering units can reduce filtration rate.
• Polycystic kidney disease: An inherited condition where cysts grow in the kidneys and gradually impair function.
• Prolonged NSAID or nephrotoxic drug use: Regular use of certain medications can damage the kidneys over time.

Symptoms of a significantly low eGFR include fatigue, trouble concentrating, poor appetite, trouble sleeping, muscle cramps, swollen feet and ankles, puffy eyes, dry or itchy skin, and needing to urinate more frequently (especially at night). Many people with mildly reduced eGFR feel completely fine, which is why testing is so important.

If your eGFR is low, your doctor will typically order urine tests (looking for protein or blood), repeat the blood test to confirm the result, check blood pressure, and possibly order kidney imaging. The combination of eGFR and urine albumin results determines both the diagnosis and the stage of kidney disease.

When Should You Get Tested?

eGFR is automatically calculated and reported whenever a creatinine blood test is ordered, so you may already have this number on past lab reports. Testing is especially important if:

• You have diabetes (type 1 or type 2), which is the leading cause of kidney disease.
• You have high blood pressure, the second leading cause of kidney disease.
• You have a family history of kidney disease or kidney failure.
• You are over 60, since kidney function naturally declines with age.
• You are taking medications that could affect the kidneys, such as NSAIDs, lithium, or certain chemotherapy drugs.
• You have heart disease, since heart and kidney health are closely linked.
• You have had a previous episode of acute kidney injury.

The National Kidney Foundation recommends that people with risk factors get their eGFR checked at least once a year.

How to Improve Your Levels

If your eGFR is lower than it should be, these steps can help slow further decline and may even improve your numbers over time:

• Control blood pressure. Aim for a target below 130/80 mmHg (or whatever goal your doctor sets). ACE inhibitors and ARBs are often preferred because they protect the kidneys while lowering blood pressure.
• Manage blood sugar. If you have diabetes, keeping your HbA1c in target range significantly reduces the risk of kidney damage progression.
• Stay hydrated. Chronic dehydration forces your kidneys to work harder. Drink enough water so that your urine is a pale straw color.
• Eat a kidney-friendly diet. Emphasize fruits, vegetables, whole grains, and lean proteins. If your kidney disease is more advanced, your doctor may recommend limiting sodium, potassium, and phosphorus.
• Exercise regularly. Aim for at least 150 minutes of moderate activity per week. Walking, cycling, and swimming are all excellent options.
• Quit smoking. Smoking constricts blood vessels and reduces blood flow to the kidneys, accelerating damage.
• Limit NSAID use. Ibuprofen, naproxen, and similar drugs can harm the kidneys, especially with regular use. Use acetaminophen for pain when possible, and always check with your doctor.
• Maintain a healthy weight. Obesity increases the risk of diabetes and hypertension, both of which damage kidneys.

Frequently Asked Questions

Q: Can eGFR go back up once it has dropped?

It depends on the cause. If the drop was caused by something reversible — like dehydration, a medication, or a urinary blockage — eGFR can absolutely recover once the issue is addressed. In chronic kidney disease, significant recovery is less common, but lifestyle changes and medications can stabilize eGFR and slow or stop further decline. Early intervention makes a meaningful difference.

Q: Why does my lab report say ">60" instead of a specific number?

Some labs only report a specific eGFR number when it falls below 60, because values above 60 are generally considered adequate kidney function. You may see ">60" or ">90" on your report. If you want a precise number, ask your doctor — they can usually access the calculated value or request the lab to report it fully.

Q: Is eGFR accurate for everyone?

The CKD-EPI formula works well for most adults but can be less accurate in certain populations. People with very high or very low muscle mass, amputees, those on extreme diets, and individuals with rapidly changing kidney function may get results that do not perfectly reflect their true GFR. In these cases, doctors may order a cystatin C-based eGFR or a direct GFR measurement using a tracer substance for a more precise assessment.

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This content is for educational purposes only and is not medical advice. Always consult your healthcare provider about your lab results.