The estimated Glomerular Filtration Rate, or eGFR, is a routine blood test that estimates how well your kidneys are functioning. It helps healthcare providers assess kidney health and detect potential kidney disease by determining if your kidneys are filtering waste from your blood effectively. Understanding your eGFR result is an important step in managing overall health.
What eGFR Measures
Your kidneys are sophisticated organs responsible for filtering waste products and excess fluid from your blood, producing urine. Within each kidney are millions of tiny filtering units called glomeruli. These microscopic filters work continuously to remove toxins and maintain a healthy balance of substances in your body.
The “filtration rate” refers to the volume of blood that these glomeruli can clean per minute. The eGFR estimates this rate, indicating how efficiently your kidneys are performing their filtering duties.
How eGFR is Calculated
The eGFR is not a direct measurement but rather a calculated estimate derived from a blood test. The primary factor in this calculation is the level of creatinine in your blood, which is a waste product from normal muscle activity. Creatinine levels rise when kidney function declines, as the kidneys are less able to filter it out.
The calculation also considers other personal factors to improve accuracy, such as your age and sex. Historically, race was included as a variable in some eGFR formulas, such as the CKD-EPI equation, to adjust the estimate. However, medical organizations have moved to remove race from these calculations due to concerns about health disparities and the lack of a biological basis for its inclusion.
Understanding Your eGFR Results
Interpreting your eGFR result involves understanding the standard ranges that indicate different levels of kidney function. Results are expressed in milliliters per minute per 1.73 square meters (mL/min/1.73m²), which normalizes the rate to an average body surface area. A higher eGFR indicates better kidney function.
An eGFR of 90 or higher suggests normal kidney function. An eGFR between 60 and 89 indicates mildly decreased kidney function. When the eGFR falls between 45 and 59, it signifies mild to moderately decreased kidney function.
An eGFR of 30 to 44 points to moderately to severely decreased function, and an eGFR of 15 to 29 indicates severely decreased kidney function. An eGFR below 15 suggests kidney failure, meaning the kidneys have lost almost all their filtering ability. It is important to remember that a single eGFR reading is a snapshot; healthcare providers often look at trends over multiple tests to understand long-term kidney health.
Factors That Influence eGFR Levels
Several factors can influence your eGFR reading, affecting either the long-term health of your kidneys or causing temporary fluctuations. Chronic conditions are common causes of sustained low eGFR. Diabetes, for example, can damage the small blood vessels in the kidneys over time, impairing their filtering capacity. Similarly, uncontrolled high blood pressure places stress on kidney arteries, leading to reduced function.
Other factors can temporarily alter eGFR. Dehydration can cause a temporary dip in the eGFR as the kidneys work with less fluid. Consuming a high-protein meal before the test might also briefly elevate creatinine levels, influencing the calculation. Intense physical exercise can similarly increase creatinine. Certain medications, including nonsteroidal anti-inflammatory drugs (NSAIDs) and some antibiotics, can affect kidney function and, consequently, eGFR levels.
Managing a Low eGFR
If you receive a low eGFR reading, working closely with your healthcare provider is an important step. They can help identify the underlying cause and develop a personalized management plan. This often includes controlling any existing conditions that impact kidney health, such as managing blood sugar levels for diabetes or keeping blood pressure within target ranges through medication and lifestyle adjustments.
Lifestyle strategies play a role in supporting kidney health and potentially slowing the progression of kidney damage. Adopting a balanced diet with reduced sodium and controlled protein intake can ease the burden on your kidneys. Regular physical activity and avoiding substances harmful to the kidneys, such as tobacco and excessive use of NSAIDs, are important steps.