eGFR (Estimated Glomerular Filtration Rate) Blood Test

eGFR estimates how well your kidneys filter waste from blood, calculated from creatinine, age, and sex. A result of 90 or above is generally normal, while a level below 60 for three months may suggest chronic kidney disease. A healthcare provider can help interpret your result.

Estimated glomerular filtration rate (eGFR) measures how efficiently your kidneys filter waste and extra fluid from the blood. Inside each kidney, millions of tiny filtering units called nephrons contain structures called glomeruli that act like sieves, letting waste products pass into urine while keeping proteins and blood cells in circulation. Because actual GFR is difficult to measure directly, laboratories calculate an estimate using a blood test for creatinine—a waste product from muscle metabolism—combined with age and sex. This calculation, known as an eGFR equation, gives a practical estimate of overall kidney filtering capacity without requiring more invasive testing, and it is one of the most commonly used markers of kidney health.

Healthcare providers order eGFR as part of a basic or comprehensive metabolic panel, or within a kidney panel, to check how well the kidneys are working. It is commonly tested during routine checkups, before starting certain medications that are processed by the kidneys, or when monitoring conditions linked to kidney health such as diabetes, high blood pressure, or heart disease. eGFR is also used to track kidney function over time in people with known kidney concerns and to help guide medication dosing decisions. Because it is calculated from creatinine, it is usually reviewed alongside creatinine results for a fuller picture.

Adult eGFR results are generally grouped into normal, mildly decreased, and reduced categories, though ranges can vary somewhat by laboratory and the specific calculation method used. A single eGFR reading is a snapshot, and trends across multiple tests often matter more than one isolated result. The table below shows general adult reference categories; your own lab report may present its reference values slightly differently.

An eGFR value that is higher than typical for someone's age is not usually flagged as a problem the way many other lab markers are, since a high estimate often simply reflects strong kidney filtering capacity. Younger adults and people with more muscle mass sometimes have eGFR values above 90. Pregnancy can also raise eGFR because blood flow to the kidneys increases during this time. A diet high in protein, especially close to testing, may temporarily raise the estimate because creatinine production and clearance can shift.

In some cases, an unusually elevated eGFR can reflect hyperfiltration, a pattern sometimes seen in early stages of diabetes or obesity, where the kidneys filter blood at a faster-than-typical rate before other changes develop. Certain medications and supplements that affect muscle breakdown or hydration status can also influence the creatinine level used in the calculation, which in turn affects the eGFR result. Because eGFR is a calculated estimate rather than a direct measurement, values at either end of the range are best interpreted alongside other markers such as creatinine, BUN, and urine tests, and discussed with a healthcare provider rather than viewed in isolation.

An eGFR below the typical adult range can happen for many reasons, some temporary and some longer term. Dehydration, a recent illness, or reduced blood flow to the kidneys can lower eGFR for a short time, and the value often returns toward normal once the underlying cause resolves. Certain medications, including some pain relievers and blood pressure drugs, can also temporarily affect kidney filtration and lower the estimate.

A persistently low eGFR—especially a value under 60 that stays low over three months—may suggest chronic kidney disease, which can be linked to long-standing diabetes, high blood pressure, or other conditions that affect the kidneys over time. Age-related decline in kidney function can also play a role, since eGFR tends to decrease gradually as people get older. A sudden drop in eGFR can occur with acute kidney injury, which may need prompt medical evaluation. Because many factors influence this calculated value, a low result is usually followed up with repeat testing and additional markers like creatinine and urine albumin.

eGFR is closely tied to creatinine, since creatinine is the main input used to calculate it; rising creatinine generally corresponds to falling eGFR. Other related markers, such as BUN, urea, and uric acid, can offer additional context about kidney function and are sometimes ordered together. Muscle mass, age, sex, diet, hydration status, and intense exercise can all influence creatinine levels and therefore the calculated eGFR, even when kidney function itself hasn't changed. Some medications and supplements can also affect the result. Because laboratories may use slightly different eGFR equations or reference values, results from different labs are not always directly comparable, and tracking trends from the same laboratory over time can be more informative than a single measurement.

If your eGFR result falls outside the typical range, consider discussing it with a healthcare provider, who can review your full health history, medications, and other lab results to put the number in context. Repeat testing is often used to confirm whether a change is temporary or ongoing. Seek prompt medical attention if a low eGFR is accompanied by symptoms such as significant swelling, marked changes in urination, confusion, or shortness of breath. Uploading a lab report to MediWing can help you see your eGFR alongside related kidney markers and track how results change over time, in plain language, though this is educational and does not replace guidance from your clinician.