eGFR Calculator (CKD-EPI 2021 Creatinine-Cystatin C)
Using the 2021 CKD-EPI Creatinine and Cystatin C Formula — Assess Your Kidney Function
Start eGFR Calculation (2021 Formula)
Formula Details
eGFR = 135 × (Scr/A)B × (ScysC/C)D × 0.9961Age
(Result is multiplied by 0.963 if female)
| Sex | Serum Creatinine (Scr) | Serum Cystatin C (ScysC) | A | B | C | D |
|---|---|---|---|---|---|---|
| Female | ≤ 0.7 mg/dL | ≤ 0.8 mg/L | 0.7 | -0.219 | 0.8 | -0.323 |
| > 0.7 mg/dL | ≤ 0.8 mg/L | 0.7 | -0.544 | 0.8 | -0.323 | |
| ≤ 0.7 mg/dL | > 0.8 mg/L | 0.7 | -0.219 | 0.8 | -0.778 | |
| > 0.7 mg/dL | > 0.8 mg/L | 0.7 | -0.544 | 0.8 | -0.778 | |
| Male | ≤ 0.9 mg/dL | ≤ 0.8 mg/L | 0.9 | -0.144 | 0.8 | -0.323 |
| > 0.9 mg/dL | ≤ 0.8 mg/L | 0.9 | -0.544 | 0.8 | -0.323 | |
| ≤ 0.9 mg/dL | > 0.8 mg/L | 0.9 | -0.144 | 0.8 | -0.778 | |
| > 0.9 mg/dL | > 0.8 mg/L | 0.9 | -0.544 | 0.8 | -0.778 |
About eGFR and the 2021 CKD-EPI Creatinine-Cystatin C Formula
What is Estimated Glomerular Filtration Rate (eGFR)?
The Estimated Glomerular Filtration Rate (eGFR) is a key indicator of kidney function. It measures how well your kidneys are filtering waste products from your blood, specifically estimating the volume of blood filtered by the glomeruli (tiny filters in the kidneys) per minute. This value is standardized to a body surface area of 1.73m² (mL/min/1.73m²).
The CKD-EPI 2021 Creatinine-Cystatin C Formula
This calculator uses the 2021 Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation that incorporates both serum creatinine (SCr) and serum cystatin C (SCysC). This combined equation is generally recommended as it provides more accurate eGFR estimates across diverse populations compared to equations based on creatinine or cystatin C alone. A key feature of the 2021 CKD-EPI equations is that they do not include race as a variable in the calculation, aiming to promote health equity in kidney disease assessment.
Cystatin C is another protein produced by the body and filtered by the kidneys. Its levels are less affected by muscle mass, age, and diet compared to creatinine, making it a valuable marker for kidney function, especially when used in conjunction with creatinine.
Clinical Significance of eGFR Values (Based on KDIGO Guidelines) for Kidney Function
eGFR values are commonly used to stage Chronic Kidney Disease (CKD):
- Stage G1: eGFR ≥ 90 mL/min/1.73m² (Normal or high, but other evidence of kidney damage may be present)
- Stage G2: eGFR 60–89 mL/min/1.73m² (Mildly decreased)
- Stage G3a: eGFR 45–59 mL/min/1.73m² (Mild to moderately decreased)
- Stage G3b: eGFR 30–44 mL/min/1.73m² (Moderate to severely decreased)
- Stage G4: eGFR 15–29 mL/min/1.73m² (Severely decreased)
- Stage G5: eGFR < 15 mL/min/1.73m² (Kidney failure)
Note: A single eGFR result does not fully determine your kidney function status. Doctors consider other clinical indicators and medical history. This calculator is an estimation tool.
References:
- Inker LA, Eneanya ND, Coresh J, et al. New Creatinine- and Cystatin C–Based Equations to Estimate GFR without Race. N Engl J Med 2021; 385:1737-1749.
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1-150. (General guidelines for interpreting eGFR)
Frequently Asked Questions (FAQ)
eGFR stands for Estimated Glomerular Filtration Rate. It is a measure of how well your kidneys are filtering wastes from your blood. An eGFR blood test isn't a direct measurement but rather a calculation derived from a blood work panel, specifically your serum creatinine level, and in newer formulas like the CKD-EPI 2021, also your serum cystatin C level. Your age and sex are also factored into this eGFR calculator to estimate your kidney function.
This eGFR calculator uses the 2021 CKD-EPI Creatinine-Cystatin C formula. This equation estimates GFR using serum creatinine, serum cystatin C, age, and sex. It is considered more accurate across diverse populations than older formulas (like MDRD or the 2009 CKD-EPI) and notably does not include a race adjustment, promoting more equitable assessment of kidney function.
Your eGFR levels provide an insight into your kidney health. An eGFR normal range is typically 90 mL/min/1.73m² or higher, indicating normal kidney function, provided there are no other signs of kidney damage. A low eGFR (e.g., below 60 mL/min/1.73m² for three months or more) may suggest chronic kidney disease (CKD). The egfr meaning of specific values is best discussed with your doctor, as they can interpret your eGFR test result in the context of your overall health. For example, an eGFR blood test low result needs medical evaluation. While less common, a very high eGFR is usually not a concern but should also be reviewed by a doctor. This eGFR calculator helps stage kidney disease based on these levels, as detailed in the 'About eGFR' section.
Serum Cystatin C (SCysC) is a protein produced by cells throughout your body. Like creatinine, it is filtered by the kidneys. SCysC levels are generally less affected by factors like muscle mass, age, or diet compared to serum creatinine. Using SCysC in combination with creatinine in the 2021 CKD-EPI formula can provide a more stable and accurate eGFR meaning and assessment of kidney function, especially in certain populations where creatinine-only estimates might be less precise.
A low eGFR or an eGFR blood test low result indicates that your kidneys may not be filtering blood as well as they should. Common causes for a persistently low eGFR include diabetes, high blood pressure, recurrent kidney infections, autoimmune diseases affecting the kidneys, or certain medications. It is crucial to consult your doctor to understand the cause of a low eGFR and discuss appropriate management. This eGFR calculator is a tool for estimation, not diagnosis.
This eGFR calculator uses the 2021 CKD-EPI formula that combines both serum creatinine and serum cystatin C. Older formulas, such as the MDRD or the 2009 CKD-EPI (which often only used creatinine), might provide different estimates. The 2021 equations are designed to improve accuracy across a wider range of GFRs and populations. A significant difference is that the 2021 formulas do not use a race coefficient, aiming for more equitable kidney health assessment.
No, this specific eGFR calculator and the 2021 CKD-EPI Creatinine-Cystatin C formula are validated for adults (age 18 and older) and are not intended for pediatric use. Kidney function during pregnancy also requires specialized assessment by a healthcare professional. Different formulas and approaches are used for these populations.
The frequency of an eGFR blood test depends on your individual health, risk factors for kidney disease (such as diabetes, hypertension, or family history), and your doctor's recommendations. If you have known kidney disease, your doctor will advise on a monitoring schedule. For general screening or if you have risk factors, regular blood work that includes an eGFR test may be part of your health check-ups. Always follow your doctor's advice on testing frequency for your eGFR levels.
The results provided by this eGFR calculator are for informational purposes only and cannot replace professional medical advice, diagnosis, or treatment for your kidney function.
Calculation results are based on the CKD-EPI 2021 creatinine and cystatin C formula, which has its limitations and may not be suitable for all individuals (e.g., age under 18, pregnancy, abnormal muscle mass, special diets, acute changes in renal function, or issues with serum creatinine measurement).
Any decisions regarding your health status should be made after consulting a qualified healthcare professional. Do not self-diagnose or adjust treatment plans based solely on the results from this eGFR calculator.
This website assumes no liability for any direct or indirect loss arising from the use of the information provided by this GFR calculator tool.