Frequently Asked Questions
Everything you need to know about GFR and kidney function
The GFR Calculator estimates the Glomerular Filtration Rate (eGFR), which is a critical measure of kidney function. It assesses how well your kidneys filter waste and excess fluids from your blood, specifically estimating the volume of blood that is filtered per minute per 1.73 m² of body surface area. This measurement helps in diagnosing and monitoring chronic kidney disease (CKD).
To use the GFR Calculator, you need to input your serum creatinine level, age, biological sex, and race. These variables are crucial as they influence kidney function and the estimation of eGFR. After entering the data, the calculator will provide your eGFR in mL/min/1.73 m² and classify your kidney function according to the stages of CKD.
The GFR Calculator utilizes the CKD-EPI (2009) and MDRD 4-variable equations for estimating eGFR. These formulas incorporate serum creatinine, age, biological sex, and race to provide a more accurate assessment of kidney function. Each formula has been validated across diverse populations, making them reliable tools in clinical settings.
The results from the GFR Calculator indicate your estimated Glomerular Filtration Rate, which reflects how well your kidneys are functioning. The output includes your eGFR value and a corresponding CKD stage classification, ranging from Stage 1 (normal or high) to Stage 5 (kidney failure). This classification helps health professionals assess the severity of kidney impairment and guide treatment decisions.
Normal eGFR values are typically above 90 mL/min/1.73 m², indicating healthy kidney function. Values between 60 and 89 mL/min/1.73 m² may suggest mild kidney damage, while values below 60 indicate a decline in kidney function that requires monitoring and potential intervention. It's important to consider eGFR results in conjunction with other health indicators and medical history.
While the GFR Calculator is a valuable tool, it has limitations, particularly regarding the accuracy of eGFR estimations in certain populations. Factors like muscle mass, hydration status, and acute illnesses can influence serum creatinine levels, potentially skewing results. Additionally, the calculator may not be as reliable for individuals with very low or very high body mass index (BMI), or for those under 18 years of age.
The GFR Calculator is primarily designed for adults who may be at risk for chronic kidney disease, including those with diabetes, hypertension, or a family history of kidney issues. Healthcare providers often use it to evaluate kidney function in patients undergoing treatment for relevant conditions. However, it can also be beneficial for patients wanting to monitor their renal health proactively.
The frequency of using the GFR Calculator can vary based on individual health factors and risk levels. Generally, it is advisable for individuals with known kidney disease or risk factors to use the calculator annually or more frequently if their health status changes. Regular monitoring helps track kidney function over time and informs necessary adjustments to treatment plans.
You should consult a doctor if your eGFR results indicate a value below 60 mL/min/1.73 m², or if there is a significant drop in your eGFR compared to previous measurements. Additionally, if you experience symptoms such as swelling, changes in urination, or fatigue, it's important to seek medical advice. A healthcare professional can provide further evaluation and discuss potential next steps based on your kidney function status.
Race is included in the GFR Calculator's inputs because research has shown differences in serum creatinine levels and kidney function markers among different racial groups. This inclusion helps improve the accuracy of eGFR estimations, as certain populations may metabolize creatinine differently. However, it is essential to approach these categorizations sensitively and recognize that kidney health can vary greatly among individuals.
The GFR Calculator is designed for use in adults and is not validated for children or adolescents. Its formulas rely on factors like age and body surface area, which differ significantly in younger populations. For pediatric patients, specialized pediatric nephrology assessments are recommended for accurate kidney function evaluation.
The GFR Calculator provides an estimated eGFR based on serum creatinine and specific demographic factors, while other tests, such as a 24-hour urine collection, measure kidney function more directly by assessing actual creatinine clearance. However, the calculator is more convenient and non-invasive, making it a useful initial screening tool. For more precise evaluations, especially in complicated cases, additional tests may be warranted.
If your eGFR indicates Stage 3 CKD or higher, it is crucial to schedule an appointment with your healthcare provider for further evaluation and management. This stage indicates moderate to severe kidney damage, which may require lifestyle changes, medication, or specialist referrals. Early intervention can help slow the progression of kidney disease and improve outcomes.
To potentially improve your eGFR results, consider adopting a healthy lifestyle that includes a balanced diet low in sodium, maintaining optimal blood pressure, and engaging in regular physical activity. Staying hydrated and managing conditions like diabetes and hypertension effectively also play a crucial role. Consulting with a healthcare provider or a registered dietitian can help you create a personalized plan to support kidney health.