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Kidney Function
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Currently under review
Pending specialist review and validation.
The estimated glomerular filtration rate, or eGFR, is a calculation that estimates how well your kidneys are filtering waste and extra fluid from your blood. It is derived from a blood creatinine test along with information such as your age and sex to estimate overall kidney filtering capacity. Modern formulas are designed to reflect kidney function across diverse populations.
eGFR is an estimate rather than a direct measurement. It is standardized to an average body size so that results can be compared over time and across people. Your clinician may interpret eGFR together with urine tests, blood pressure, and other labs to build a complete picture of kidney health.
Clinicians use eGFR to detect kidney disease early, determine its stage, and monitor changes over time. It helps guide decisions about medications and doses that are cleared by the kidneys, assess readiness for imaging studies or surgeries, and evaluate risks during acute illnesses.
When eGFR is persistently lower than expected, it can signal chronic kidney disease and a higher risk of complications such as fluid and electrolyte problems, anemia, bone and mineral changes, and heart and blood vessel disease. Tracking eGFR trends can help you and your care team act early to protect kidney health and reduce related risks.
A higher eGFR generally indicates better kidney filtration, while a lower eGFR suggests reduced kidney function. A single result can be influenced by hydration, recent illness, strenuous exercise, or laboratory method differences. Your clinician will interpret your eGFR in context, including symptoms, blood pressure, and other tests.
If a result is unexpected, your clinician may repeat testing to confirm and look at the pattern over time. They may also check urine albumin, electrolytes, and acid base status. When results do not fit your clinical picture, a cystatin C based estimate, a direct measurement of kidney filtration, or a referral to a kidney specialist may be considered. You may be advised on lifestyle measures, blood pressure and diabetes control, and medication adjustments to support kidney health.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
Dehydration, vomiting, fever, or sudden illness can temporarily change creatinine levels and eGFR. Repeating the test after recovery often provides a more reliable baseline.
Creatinine comes from muscle. Very high or very low muscle mass, heavy exercise, large meat meals, or creatine supplements can shift creatinine and affect eGFR without a true change in kidney function.
Drugs such as trimethoprim, cimetidine, cobicistat, and dolutegravir can raise blood creatinine by reducing its secretion in the kidney, lowering eGFR estimates even when actual filtration has not changed.
Differences in creatinine assays and the specific estimating equation used can slightly alter eGFR. Using the same lab and method over time helps with consistent trending.
Normal physiologic changes in pregnancy alter kidney filtration and creatinine levels. Creatinine based eGFR may be less reliable, so clinicians may use alternative assessments when needed.
Amputations, advanced frailty, neuromuscular conditions, or bodybuilders may have creatinine production that is not typical, making eGFR less accurate. A cystatin C based estimate can help in these situations.
Fasting is usually not required, but avoiding unusually heavy exercise and very large meat meals before the blood draw can reduce short term fluctuations in creatinine and eGFR.
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