eGFR: Estimated Kidney Filtration and What Your Number Really Means
Overview
eGFR is a calculated estimate of how well your kidneys are filtering waste from your blood. It turns your creatinine level, age, and other factors into a single number that helps track kidney function over time. In this glossary you will see what eGFR actually measures, how it connects to Creatinine, BUN, and urine Albumin, how to think about different eGFR ranges without panic, what can nudge your result up or down, how kidney friendly patterns like DASH can support long term health, and when it is time to walk the number through with a clinician.
What eGFR is and why it matters
eGFR stands for estimated glomerular filtration rate. It is a calculation that uses your blood creatinine level, age, and other factors to estimate how many milliliters of blood your kidneys can filter per minute.
Key ideas:
kidney filters are called glomeruli
eGFR is an estimate of how much blood they are cleaning each minute
higher eGFR usually means better filtration, lower eGFR means reduced kidney function
Because it is standardized and easy to trend, eGFR is used to stage chronic kidney disease and to monitor how kidney function changes over time. It is not a perfect measure, but it is very useful for seeing whether things are stable, improving, or declining.
What your eGFR result can tell you
Your eGFR value can help answer questions like:
Are my kidneys filtering at a level that is expected for my age and size
Is my kidney function stable, drifting down, or clearly reduced
Do my blood pressure, blood sugar, and medications seem to be protecting my kidneys or putting extra stress on them
eGFR is especially helpful when compared over time and when interpreted alongside creatinine, BUN, urine albumin, blood pressure, and your health history. One slightly low value during dehydration or illness may look very different from a steady decline over several years.
How to read high and low eGFR
eGFR works as a rough gauge of kidney filtration. Numbers are not exact, but the direction and range matter.
When eGFR is low
A lower eGFR can mean:
Your kidneys are not filtering as well as they should, either due to long term damage or a temporary problem
Chronic conditions such as high blood pressure or diabetes may be affecting the kidneys
There is less reserve if you become sick, dehydrated, or take medications that stress kidney function
Lower eGFR values are used to stage chronic kidney disease. The lower the eGFR and the longer it stays low, the higher the risk that waste and fluid can build up and that heart and vessel risk can rise.
When eGFR is in a normal or higher range
A normal or higher eGFR generally means:
Your kidneys are filtering at a level that is considered acceptable for your age
You have more reserve if you become sick or need short term medications that can affect kidney function
In very muscular people or during pregnancy, eGFR formulas can be less accurate. In older adults, a mild drop in eGFR can sometimes reflect normal aging, but it still deserves attention as part of the bigger risk picture.
What can affect your eGFR result
Because eGFR is calculated from creatinine and other inputs, anything that changes those inputs or kidney performance can move the number. Common influences include:
Kidney health and blood pressure
Long term high blood pressure and diabetes are leading causes of reduced eGFR. Good control of both is key for slowing kidney decline.Hydration and acute illness
Dehydration, severe infections, or other acute illnesses can temporarily lower eGFR by reducing blood flow to the kidneys. Rehydration and recovery can bring it back toward baseline.Muscle mass and diet
More muscle can mean higher creatinine and a slightly lower estimated eGFR, even when kidneys are healthy. A large meat heavy meal before a test can also affect creatinine and the calculated eGFR.Medications and contrast dyes
Some pain medicines, certain blood pressure medications, and imaging contrast dyes can affect kidney filtration, sometimes temporarily. That is why eGFR is often checked before and after these are used.Age
eGFR tends to decline gradually with age, even in the absence of obvious kidney disease. The key question is whether the level is appropriate for your age and whether the decline is slow and stable or faster than expected.
Looking at eGFR together with context from the last few weeks and months helps make sense of the number.
When to talk to a clinician about eGFR
You should review your eGFR result with a clinician when:
eGFR is clearly below the normal range for your age, or lower than 60 on more than one test
Your eGFR is falling over time, even if it started in the normal range
You have conditions like diabetes, high blood pressure, or heart disease and you want to understand how your kidneys are doing
You are starting or using medications that can affect kidney function, or you have protein in your urine or swelling in your legs or around your eyes
A clinician can place eGFR next to creatinine, BUN, urine albumin, electrolytes, blood pressure, blood sugar, and your full history. From there, they can help decide whether the result reflects chronic kidney disease, a temporary issue like dehydration, or something else, and what steps make the most sense to slow or prevent further decline.
eGFR in one view
eGFR is an estimated score of how well your kidneys are filtering waste from your blood and is one of the main tools for spotting and tracking kidney problems. It is not a perfect measurement, but together with creatinine, BUN, urine tests, blood pressure, and your medical history it gives a clear sense of whether your kidneys are stable or under strain. A persistently low or falling eGFR is an early signal to protect your kidneys by tuning blood pressure, blood sugar, medications, hydration, and lifestyle with a clinician rather than waiting for more serious symptoms to develop.
