What Does eGFR Mean in a Lab Result? A Plain English Guide
You got your blood work back and there's a number called "eGFR" that you've never noticed before. Maybe it's flagged as low. Maybe your doctor mentioned it in passing. Either way, you're wondering what it means and whether you should be worried. This guide explains everything in plain, simple language.
What is eGFR?
eGFR stands for estimated Glomerular Filtration Rate. That's a mouthful, so let's break it down. Your kidneys contain tiny filters called glomeruli. Their job is to clean your blood by filtering out waste products, which then leave your body as urine. The eGFR is an estimate of how well those filters are working.
The "estimated" part is important. Your eGFR isn't measured directly. Instead, it's calculated from a blood test called creatinine (a waste product your muscles produce), combined with your age, sex, and sometimes body size. A formula turns these inputs into a single number that represents your kidney function.
The simple explanation
Think of your kidneys like a coffee filter. A new filter works perfectly — water flows through quickly and cleanly. Over time, the filter gets clogged and water flows through more slowly. eGFR measures how fast your kidney "filter" is working. A higher number means better flow. A lower number means the filter is slowing down.
A healthy eGFR is generally 90 or above. The number represents how many millilitres of blood your kidneys can filter per minute. So an eGFR of 90 means your kidneys are filtering about 90 millilitres of blood every minute — which is normal and healthy.
What the numbers mean
Here's what different eGFR ranges typically indicate. Remember, these are general guidelines — your doctor interprets your specific number in the context of your overall health.
Your kidneys are working normally. This is the healthy range for most people. Many labs will simply report this as ">60" or ">90" since the exact number is less important when kidney function is good.
Mildly reduced kidney function. This is common as people age and often doesn't cause any symptoms or problems. Your doctor may want to monitor it over time but usually no treatment is needed at this stage.
Moderately reduced kidney function. At this level your kidneys aren't filtering waste as efficiently as they should. You probably won't feel symptoms yet, but your doctor will likely want to investigate the cause and monitor more closely.
Severely reduced kidney function. At this level the kidneys are struggling significantly. You may start to notice symptoms like fatigue, swelling, or changes in urination. Your doctor will be actively managing your kidney health and may refer you to a nephrologist (kidney specialist).
Kidney failure or near failure. The kidneys can no longer adequately filter waste from the blood. Treatment options such as dialysis or a kidney transplant are typically discussed at this stage. This requires close medical supervision.
What does a low eGFR mean?
A low eGFR means your kidneys aren't filtering blood as well as they could be. But before you panic, there are some important things to understand.
A single low reading doesn't necessarily mean you have kidney disease. Many things can temporarily lower your eGFR, including dehydration, certain medications, a recent intense workout, or even eating a large amount of protein before the test. Your doctor will typically repeat the test after a few weeks to see if the number stays low or returns to normal.
If your eGFR is consistently low across multiple tests — usually three months apart — that's when your doctor may diagnose chronic kidney disease (CKD). Even then, CKD is a spectrum, and many people with mild to moderate CKD live completely normal lives with simple monitoring.
Common causes of low eGFR
The two most common causes of reduced kidney function are high blood pressure and diabetes. Together, these account for the majority of kidney disease cases. Other causes include certain medications that affect the kidneys over time (like long-term use of some pain relievers), kidney infections, autoimmune conditions, and genetic conditions like polycystic kidney disease.
Age is also a factor. It's completely normal for eGFR to decline gradually as you get older. A 70-year-old with an eGFR of 65 might be perfectly healthy — that number is expected for their age. This is one reason why your doctor looks at the full picture, not just the number.
Can eGFR fluctuate?
Yes — eGFR can vary from test to test. It's not a fixed number. Dehydration can temporarily lower it. So can strenuous exercise, a high-protein meal eaten before the blood draw, or certain medications. Even the time of day can affect your creatinine level, which in turn affects the eGFR calculation.
This is why doctors don't usually make decisions based on a single eGFR reading. They look at the trend over time. If your eGFR dropped from 85 to 78 between two tests, that could just be normal variation. But if it's been steadily declining from 85 to 70 to 55 over a couple of years, that's a pattern worth investigating.
One low eGFR reading is a data point. A pattern of declining eGFR over several tests is information. Don't panic over a single number — but do follow up with your doctor if they ask you to retest.
Can you improve your eGFR?
In some cases, yes. If the low eGFR was caused by something temporary like dehydration or medication, fixing the underlying cause can bring the number back up. If it's related to high blood pressure or diabetes, managing those conditions well can slow or even stop further decline.
General kidney-friendly habits include staying well hydrated, managing blood pressure and blood sugar, limiting salt intake, avoiding excessive use of over-the-counter pain relievers (especially NSAIDs like ibuprofen), not smoking, and maintaining a healthy weight. Your doctor can give you specific guidance based on your situation.
It's worth knowing that once kidney function is significantly reduced, it typically can't be fully restored. But catching it early and making lifestyle changes can make a real difference in slowing the progression.
Questions to ask your doctor
If your eGFR came back low or flagged on your lab results, here are some questions worth asking at your next appointment. What is my exact eGFR number and what stage does that put me at? Should I have a repeat test to confirm, and when? What might be causing my eGFR to be low? Are any of my current medications affecting my kidney function? What changes should I make to protect my kidneys? Should I see a kidney specialist?
If you notice sudden symptoms like severe swelling in your legs, face, or hands, a dramatic change in how much or how often you urinate, blood in your urine, persistent nausea or vomiting, or severe fatigue — contact your doctor immediately or go to urgent care. These could indicate a rapid change in kidney function that needs prompt attention.
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Try MedClear AI freePublished by MedClear AI · getmedclear.com · For informational purposes only. Always consult your healthcare team for advice specific to your situation.