Understanding Your Kidney Function Score Guide

What Your Kidney Function Score Means

Your kidney function score, also called your estimated glomerular filtration rate (eGFR), is a number that tells you how well your kidneys are filtering waste from your blood. Think of your kidneys as tiny cleaning machines. They filter about 120 to 150 quarts of blood every day to remove waste and extra water, which become urine. Your eGFR score is measured in milliliters per minute per 1.73 square meters of body surface area, written as mL/min/1.73m². The higher your eGFR number, the better your kidneys are working.

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Most labs report eGFR scores ranging from above 90 to below 15. A score of 90 or higher typically means your kidneys are working well. If your score drops below 60 and stays low for three months or more, this indicates your kidneys may not be working as well as they should. However, one low score doesn't always mean you have kidney disease. Your doctor may want to repeat the test to confirm the result.

Your eGFR is calculated based on your creatinine level, which is a waste product your body makes from muscle activity. Creatinine builds up in your blood when your kidneys aren't filtering properly. The calculation also considers your age, sex, and race because these factors affect how creatinine levels relate to kidney function. A blood test is the most common way to measure creatinine and calculate your eGFR.

Understanding your kidney function score is the first step toward managing your health. Many people don't realize they have kidney problems because early stages often have no symptoms. By learning what your score means, you can work with your doctor to catch any issues early. Regular testing becomes especially important if you have risk factors like diabetes, high blood pressure, or a family history of kidney disease.

Practical Takeaway: Ask your doctor to explain your specific eGFR number and what it means for your health. Request a copy of your test results and keep track of your scores over time to spot any changes.

The Five Stages of Kidney Disease

Kidney disease is divided into five stages based on your eGFR score. Understanding these stages helps you and your doctor plan appropriate care. Stage 1 begins when your eGFR is 90 or higher, meaning your kidneys are working normally or nearly normally. However, if you have other signs of kidney damage—such as protein in your urine or imaging abnormalities—your doctor may still diagnose early kidney disease even with a normal eGFR score.

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Stage 2 represents mild loss of kidney function, with an eGFR between 60 and 89. At this stage, your kidneys are still doing most of their job. Many people at this stage have no symptoms and don't realize they have any kidney concerns. However, your doctor may want to monitor your kidney function regularly and help you manage any risk factors like blood pressure or blood sugar levels.

Stage 3 is divided into two parts: Stage 3a with an eGFR of 45 to 59, and Stage 3b with an eGFR of 30 to 44. Both represent moderate loss of kidney function. At this stage, waste products may start building up in your blood, and some people begin to notice symptoms like fatigue, swelling in the hands or feet, or frequent urination. Your doctor will likely recommend more frequent check-ups and blood pressure monitoring.

Stage 4 indicates severe loss of kidney function, with an eGFR between 15 and 29. At this point, your kidneys are working at only about 15 to 29 percent of normal capacity. Symptoms become more noticeable, and your doctor will begin preparing you for the possibility of kidney failure. This is when treatment options like dialysis or kidney transplant planning may be discussed.

Stage 5 is kidney failure, also called end-stage renal disease (ESRD), with an eGFR below 15. At this stage, your kidneys cannot filter waste adequately, and you will likely need dialysis or a kidney transplant to survive. Many people reach this stage over several years, giving time for planning and preparation.

Practical Takeaway: Once you know your eGFR score, identify which stage applies to you. Ask your doctor what monitoring schedule makes sense for your specific stage and what symptoms to watch for.

How Your eGFR Is Calculated

Your eGFR is not measured directly. Instead, it's calculated using your creatinine level and other personal information. Creatinine is a chemical waste product that your muscles produce constantly as they use energy. Your kidneys filter creatinine out of your blood and into your urine. When your kidneys work well, creatinine levels stay low and stable. When kidney function declines, creatinine builds up in your blood.

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The most common formula used to calculate eGFR is called the CKD-EPI equation, developed by the Chronic Kidney Disease Epidemiology Collaboration. This formula was updated in 2021 to improve accuracy. The formula takes into account your serum creatinine (the creatinine level in your blood), your age, your sex, and your race. The result is an estimate of how many milliliters of waste your kidneys can filter each minute.

Your doctor orders a blood test to measure creatinine. The blood sample is sent to a laboratory where technicians measure the exact creatinine concentration. The laboratory then uses the CKD-EPI equation to calculate your eGFR automatically. Most modern lab reports include both your serum creatinine number and your calculated eGFR.

It's important to understand that eGFR is an estimate, not a perfect measurement. Several factors can affect the accuracy of this calculation. Muscle mass influences creatinine production, so people with larger muscles may have higher creatinine levels even if their kidneys work normally. Older adults, people with low muscle mass, people who are pregnant, and people with severe malnutrition may have less accurate eGFR estimates. Some medications and supplements can also temporarily affect creatinine levels.

Because of these variables, doctors don't rely on a single eGFR result. Instead, they look at trends over time. If your eGFR drops significantly and stays low, it suggests actual kidney function decline. If a single result seems unusually low compared to your previous results, your doctor may repeat the test to confirm.

Practical Takeaway: When you receive lab results, look for both your creatinine level and your eGFR. Ask your doctor to explain whether your result is new or part of a pattern. If your eGFR has changed significantly, ask whether your doctor recommends repeat testing.

Risk Factors That Affect Kidney Function

Several conditions and lifestyle factors put you at higher risk for developing kidney problems. Diabetes is the leading cause of kidney disease in the United States, accounting for about one-third of all cases. High blood sugar levels damage the delicate blood vessels in your kidneys over time. According to the National Kidney Foundation, about 1 in 4 adults with diabetes develop kidney disease.

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High blood pressure is the second leading cause of kidney disease, responsible for about one-quarter of cases. High blood pressure damages blood vessels in your kidneys, reducing their ability to filter waste. This creates a dangerous cycle: damaged kidneys become less effective at regulating blood pressure, which further damages kidney function. Managing blood pressure is one of the most important ways to protect your kidneys.

Other medical conditions that increase kidney disease risk include heart disease, obesity, and autoimmune diseases like lupus. Certain infections and kidney stones can also damage kidney function. If you have a family history of kidney disease, your risk is higher because you may inherit genetic factors that make you more vulnerable.

Lifestyle factors matter significantly too. Smoking increases kidney disease risk by constricting blood vessels and reducing blood flow to your kidneys. Excessive alcohol consumption can raise blood pressure and damage kidney tissue over time. A diet high in salt, sugar, and processed foods contributes to obesity, diabetes, and high blood pressure—all risk factors for kidney disease. People who are physically inactive have higher risks than those who exercise regularly.

Certain medications can affect kidney function, including some over-the-counter pain relievers like ibuprofen and naproxen, especially when used long-term. Older age increases kidney