Estimated Glomerular Filtration Rate, or eGFR, is a calculation used to assess how well the kidneys are functioning. It serves as a key indicator in monitoring kidney health and identifying potential kidney disease. While eGFR provides a valuable estimate, its readings can vary. Recognizing the factors that influence these variations is important for accurately interpreting results and making informed decisions about health.
What eGFR Represents
The eGFR measures how effectively the kidneys are filtering waste products from the blood. The kidneys contain millions of tiny filters called glomeruli, which are responsible for removing toxins and excess water to produce urine. The eGFR specifically estimates the rate at which these glomeruli are cleaning the blood.
This estimation is typically derived from a blood test that measures creatinine, a waste product from muscle breakdown. The calculation also incorporates factors such as age, sex, and body size. Historically, race was included in some eGFR calculations, but major kidney health organizations have recommended removing it due to concerns about accuracy and health inequities. A lower eGFR number can indicate reduced kidney function, suggesting that the kidneys may not be working as efficiently as they should.
Everyday Influences on eGFR Readings
Several common, non-disease related factors can lead to temporary shifts in eGFR readings. One such factor is hydration status; dehydration can temporarily lower eGFR because there is less fluid for the kidneys to filter efficiently. Dietary choices also play a role, with a high protein intake, particularly before a test, potentially causing a transient increase in creatinine levels and thus affecting the eGFR calculation.
Intense physical activity can also influence eGFR, as vigorous exercise can temporarily elevate creatinine due to increased muscle breakdown. Certain medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and some blood pressure medications, are known to impact kidney function and can lead to fluctuations in eGFR. Acute infections, by placing stress on the body, may also cause a temporary dip in eGFR values. Even the time of day a blood sample is taken can introduce minor variations, highlighting the dynamic nature of this estimate.
Assessing the Significance of eGFR Changes
Some fluctuation in eGFR readings is normal and expected, reflecting the body’s dynamic physiological processes. A change of a few points up or down, or small percentage shifts, typically falls within the range of normal biological variability. For instance, a 5-10% change between readings might not be a cause for concern on its own. It is also important to consider laboratory measurement variability, as slight differences can occur between tests.
However, a sustained drop of more than 10-15% or a significant decline observed across multiple tests may indicate a more substantial change in kidney function. For adults, an eGFR below 60 for three months or more, or an eGFR above 60 with signs of kidney damage like high albumin in urine, suggests chronic kidney disease. Healthcare providers often look for trends over time rather than focusing on a single reading. A consistent pattern of decline warrants further investigation to understand the underlying cause.
Navigating eGFR Results
When an eGFR reading fluctuates, discussing the results with a healthcare provider is crucial. They interpret the numbers in the context of an individual’s overall health history and other test results. Providers may recommend repeat testing to confirm trends and rule out temporary influences, allowing for a more accurate assessment of kidney function over time.
Reviewing current medications with a doctor is also important, as some drugs can affect eGFR. Adopting a kidney-friendly lifestyle supports overall kidney health. This includes maintaining adequate hydration, managing blood pressure and diabetes, and adhering to a balanced, healthy diet. Proactive communication ensures that any changes in eGFR are properly evaluated and addressed.
What eGFR Represents
The eGFR measures how effectively the kidneys’ glomeruli filter waste products from the blood. These tiny filters remove toxins and excess water to produce urine. The eGFR specifically estimates the rate at which these glomeruli clean the blood.
This estimation is derived from a creatinine blood test, incorporating age, sex, and body size. Historically, race was included, but major kidney health organizations now recommend removing it due to accuracy and health equity concerns. A lower eGFR number indicates reduced kidney function.
Everyday Influences on eGFR Readings
Beyond disease, several factors cause temporary eGFR shifts. Dehydration can lower eGFR due to reduced blood volume and pressure, impacting glomerular filtration. High protein intake, especially from meat before a test, can transiently increase creatinine levels, affecting the eGFR calculation.
Vigorous physical activity can elevate creatinine from muscle breakdown, influencing eGFR. Certain medications, like NSAIDs and some blood pressure drugs, impact kidney function and cause fluctuations. Acute infections, by stressing the body, may also temporarily dip eGFR values. Minor variations can even occur based on the time of day a blood sample is taken.
Assessing the Significance of eGFR Changes
Normal eGFR fluctuation reflects the body’s dynamic processes. Small percentage shifts or a few points up or down are typical biological variability. A 5-10% change between readings might not be a concern, and laboratory assay variability contributes to small shifts. eGFR naturally declines with age, even without kidney disease, averaging about 0.96 mL/min/year or 10 mL/min/decade after age 30-40.
A sustained drop over 10-15% or significant decline across multiple tests indicates a more substantial change. For adults, eGFR below 60 for three months or more, or above 60 with kidney damage signs like high albumin in urine, suggests chronic kidney disease. Providers look for long-term trends, as short-term observations may be insufficient due to fluctuations. A consistent decline warrants further investigation.
Navigating eGFR Results
When eGFR fluctuates, discussing results with a healthcare provider is paramount. They interpret numbers within your overall health history and other test results. Providers may recommend repeat testing to confirm trends and rule out temporary influences, especially with sudden changes. This ensures accurate assessment of kidney function over time.
Reviewing current medications with a doctor is important, as some drugs affect eGFR and may require dosage adjustments. Adopting a kidney-friendly lifestyle supports overall kidney health. This includes adequate hydration, managing blood pressure and diabetes, and adhering to a balanced diet. Reduced animal protein, increased fruits and vegetables, and regular exercise are generally beneficial for slowing eGFR decline.