Creatinine Calculated Glomerular Filtration Rate

Estimate your kidney's filtering capacity using the CKD-EPI creatinine equation.

eGFR Calculator

eGFR Trends Over Time (Illustrative)

eGFR Range (mL/min/1.73m²)	Description	Interpretation
≥ 90	Normal or high	Healthy kidney function, or may indicate other conditions.
60-89	Mildly decreased	May indicate kidney disease, especially if present for 3+ months.
45-59	Mild to moderately decreased	Possible kidney disease. Further investigation needed.
30-44	Moderately to severely decreased	Significant reduction in kidney function.
15-29	Severely decreased	Kidney failure is approaching.
< 15	Kidney failure	Requires immediate medical attention, often dialysis or transplant evaluation.

What is Creatinine Calculated Glomerular Filtration Rate (eGFR)?

{primary_keyword} is a vital blood test measurement that estimates how well your kidneys are filtering waste products from your blood. It's expressed in milliliters per minute per 1.73 square meters of body surface area (mL/min/1.73m²). Think of your kidneys as sophisticated filters; eGFR tells you how effectively these filters are working. A higher eGFR generally indicates healthier kidney function, while a lower eGFR suggests that your kidneys may not be filtering waste as efficiently as they should. This value is crucial for diagnosing and staging chronic kidney disease (CKD), monitoring its progression, and guiding treatment decisions. It is a more practical and widely used measure than directly measuring GFR, which is complex and invasive.

Who should use an eGFR calculator? Anyone who has had a blood test for serum creatinine should understand their eGFR. This includes individuals with:

• High blood pressure
• Diabetes
• A family history of kidney disease
• Heart disease
• Those taking medications that can affect the kidneys
• Older adults
• Anyone experiencing symptoms that might suggest kidney problems (e.g., swelling, fatigue, changes in urination).

Common misconceptions about eGFR:

• eGFR is a direct GFR measurement: eGFR is an *estimation*, not a direct measurement like inulin clearance.
• A single low eGFR means kidney failure: Kidney function can fluctuate. A diagnosis of CKD usually requires a persistently low eGFR over at least three months.
• eGFR is only for people with known kidney disease: It's a crucial screening tool for everyone, especially those with risk factors.
• Race is always a factor: Newer equations (like CKD-EPI 2021) have removed race as a variable, acknowledging its limitations and potential for bias.

Creatinine Calculated Glomerular Filtration Rate (eGFR) Formula and Mathematical Explanation

The most commonly used formula for estimating GFR is the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation. While older versions incorporated race, the 2021 update is race-free and more widely recommended.

CKD-EPI Creatinine Equation (2021) – Simplified Representation:

eGFR = 142 × min(SCr/κ, 1)^α × max(1 – 0.011 × Age) × (1.062 if female) × (1.17 if Black – note: this race coefficient is being phased out and is absent in the 2021 eGFT form)

Let's break down the variables for clarity:

Variable	Meaning	Unit	Typical Range
SCr	Serum Creatinine	mg/dL (milligrams per deciliter)	0.6 – 1.3 mg/dL (varies by lab and individual)
Age	Age of the individual	Years	1 – 120 years
κ (kappa)	Constant value specific to biological sex: 0.7 for females, 0.9 for males.	Unitless	0.7 or 0.9
α (alpha)	Exponent specific to biological sex: -0.329 for females, -0.411 for males.	Unitless	-0.329 or -0.411
min(SCr/κ, 1)	The lower value between (SCr/κ) and 1. This ensures the result doesn't exceed certain thresholds based on the SCr/κ ratio.	Unitless	Typically between 0.1 and 1
max(1 – 0.011 × Age, 0)	The higher value between (1 – 0.011 × Age) and 0. This ensures the age factor doesn't result in a negative contribution.	Unitless	Typically between 0.5 and 1
1.062 if female	A correction factor applied if the individual is biologically female.	Unitless	1.062
(1.17 if Black)	A correction factor historically applied for individuals of Black race in older CKD-EPI versions. The 2021 equation does not use this factor.	Unitless	1.17 (for older versions)

The 2021 CKD-EPI equation is designed to be more accurate across a wider range of GFR values and populations compared to older formulas like MDRD. The constants (κ and α) and the sex multiplier adjust the calculation based on known physiological differences affecting creatinine production and clearance.

Practical Examples (Real-World Use Cases)

Example 1: Routine Check-up for a Diabetic Patient

Patient Profile: Sarah, a 58-year-old female, has Type 2 diabetes and high blood pressure. She undergoes an annual physical exam.

• Age: 58 years
• Biological Sex: Female
• Serum Creatinine: 0.85 mg/dL
• Race: Non-Black (using modern standard)

Calculation (CKD-EPI 2021):

First, determine the constants for females:

• κ = 0.7
• α = -0.329

Calculate SCr/κ = 0.85 / 0.7 = 1.214

min(SCr/κ, 1) = min(1.214, 1) = 1

Calculate age factor: 1 – 0.011 × 58 = 1 – 0.638 = 0.362

max(age factor, 0) = max(0.362, 0) = 0.362

Sex factor: 1.062 (since Sarah is female)

eGFR = 142 × 1 × 0.362 × 1.062

eGFR = 142 × 0.384444 ≈ 54.6 mL/min/1.73m²

Result: eGFR ≈ 55 mL/min/1.73m²

Interpretation: Sarah's eGFR of 55 falls into the "mild to moderately decreased" category. While diabetes and hypertension are risk factors, this result warrants closer monitoring by her physician. It suggests a potential early stage of chronic kidney disease, and strategies to manage her blood sugar and blood pressure effectively become even more critical.

Example 2: Monitoring Kidney Function in an Older Male

Patient Profile: John, a 72-year-old male, has a history of heart failure and is taking multiple medications.

• Age: 72 years
• Biological Sex: Male
• Serum Creatinine: 1.1 mg/dL
• Race: Non-Black

Calculation (CKD-EPI 2021):

First, determine the constants for males:

• κ = 0.9
• α = -0.411

Calculate SCr/κ = 1.1 / 0.9 = 1.222

min(SCr/κ, 1) = min(1.222, 1) = 1

Calculate age factor: 1 – 0.011 × 72 = 1 – 0.792 = 0.208

max(age factor, 0) = max(0.208, 0) = 0.208

Sex factor: 1 (since John is male)

eGFR = 142 × 1 × 0.208 × 1

eGFR = 142 × 0.208 ≈ 29.5 mL/min/1.73m²

Result: eGFR ≈ 30 mL/min/1.73m²

Interpretation: John's eGFR of 30 falls into the "moderately to severely decreased" range. This indicates significant impairment of his kidney function. Given his age and other health conditions, this finding necessitates a thorough evaluation by a nephrologist to determine the underlying cause and discuss management options, potentially including medication adjustments or preparation for kidney replacement therapy.

How to Use This Creatinine Calculated Glomerular Filtration Rate (eGFR) Calculator

Using our eGFR calculator is straightforward and can help you understand your kidney health report.

1. Gather Your Information: You will need your most recent serum creatinine level (from a blood test, usually in mg/dL), your age in years, and your biological sex. You may also see a race listed on older lab reports, though the calculator uses the modern, race-free equation.
2. Enter Serum Creatinine: Input the value for serum creatinine exactly as it appears on your lab report. Pay attention to the units (mg/dL).
3. Enter Age: Input your current age in whole years.
4. Select Biological Sex: Choose 'Male' or 'Female' based on your biological sex.
5. Select Race (Optional/Historical): For the CKD-EPI 2021 equation, this field is not used. If you are using older equations or your doctor requested it, select the appropriate option. For modern calculations, 'Non-Black' is the standard.
6. Calculate: Click the "Calculate eGFR" button.

How to Read Results:

• Primary Result (eGFR): This is the main output, showing your estimated GFR in mL/min/1.73m².
• Intermediate Values: These confirm the inputs used in the calculation.
• Interpretation Table: Compare your eGFR value to the provided table to understand the general meaning (Normal, Mildly Decreased, Severely Decreased, etc.).

Decision-Making Guidance:

• Normal or High eGFR (≥ 90): Generally indicates good kidney function. However, if you have risk factors like diabetes or hypertension, discuss with your doctor.
• Mildly Decreased eGFR (60-89): If this level is consistent over time (3+ months), it may signal early CKD. Focus on managing risk factors and follow your doctor's advice.
• Moderately to Severely Decreased eGFR (< 60): This is a significant finding. Consult a healthcare professional promptly for further evaluation, potential causes, and treatment strategies. This might involve lifestyle changes, medication adjustments, or specialist referral.
• Very Low eGFR (< 15): Indicates kidney failure. Urgent medical management is required.

Important Note: This calculator provides an estimate for informational purposes only. It does not replace a professional medical diagnosis. Always consult with your healthcare provider for any health concerns or decisions.

Key Factors That Affect Creatinine Calculated Glomerular Filtration Rate Results

Several factors can influence your serum creatinine level and, consequently, your calculated eGFR, even if your actual kidney filtration rate hasn't changed:

1. Muscle Mass: Creatinine is a byproduct of muscle metabolism. Individuals with higher muscle mass (e.g., bodybuilders, young men) tend to produce more creatinine, potentially leading to a higher serum creatinine and a lower apparent eGFR, even with healthy kidneys. Conversely, older adults or those with muscle-wasting conditions may have lower creatinine and a falsely higher eGFR.
2. Diet: Consuming large amounts of cooked meat shortly before a blood test can temporarily increase serum creatinine levels, slightly lowering the calculated eGFR.
3. Medications: Certain drugs can interfere with creatinine measurement or affect kidney function directly. Examples include trimethoprim (an antibiotic) and cimetidine (for heartburn), which can inhibit tubular secretion of creatinine, increasing blood levels without changing GFR. Some NSAIDs or other medications can impact renal blood flow.
4. Hydration Status: Severe dehydration can temporarily reduce blood flow to the kidneys, potentially lowering GFR and increasing creatinine. Conversely, overhydration might dilute creatinine slightly.
5. Kidney Injury (Acute): Sudden damage to the kidneys (AKI) will cause a rapid rise in serum creatinine and a sharp drop in eGFR. This is distinct from chronic kidney disease (CKD).
6. Laboratory Variability: Differences in laboratory assays, calibration, and reference ranges can lead to slight variations in reported serum creatinine values. Always use values from the same lab for consistent monitoring.
7. Body Surface Area (BSA) Adjustments: While the CKD-EPI equation incorporates BSA implicitly (by dividing by 1.73m²), extreme body sizes (very tall or very short individuals) might still have some variability.
8. Conditions Affecting Creatinine Secretion: Certain medical conditions or drugs can affect how efficiently the kidneys secrete creatinine (beyond just filtering it), leading to discrepancies between calculated eGFR and true GFR.

Understanding these factors is crucial for interpreting eGFR results accurately and discussing them meaningfully with your doctor. It highlights why a single reading might not tell the whole story and why trends over time are often more informative.

Frequently Asked Questions (FAQ)

What is the difference between GFR and eGFR?

GFR (Glomerular Filtration Rate) is the actual measure of how much blood your kidneys filter each minute. eGFR (estimated Glomerular Filtration Rate) is a calculation based on your serum creatinine level, age, sex, and sometimes race, used to approximate your GFR. Direct GFR measurement is complex and rarely done outside research settings.

Is an eGFR of 60 bad?

An eGFR of 60 mL/min/1.73m² is generally considered mildly decreased. If this level is consistent for three months or more, it may indicate stage 2 Chronic Kidney Disease (CKD). It's important to discuss this result with your doctor, especially if you have risk factors like diabetes, hypertension, or a family history of kidney disease.

Can eGFR be improved?

If the eGFR decrease is due to treatable causes like uncontrolled high blood pressure, diabetes, or certain infections, then improving these underlying conditions can help stabilize or even slightly improve kidney function. However, significant damage from chronic kidney disease is often irreversible. The focus then shifts to slowing progression and managing complications.

What causes a low eGFR?

The most common causes of chronically low eGFR are diabetes and high blood pressure, which damage the small blood vessels in the kidneys over time. Other causes include glomerulonephritis (inflammation of the kidney's filtering units), polycystic kidney disease, prolonged use of certain medications (like NSAIDs), and severe dehydration or illness.

Does the CKD-EPI 2021 equation use race?

No, the CKD-EPI 2021 equation is specifically designed to be race-free. This update reflects a growing understanding that using race as a biological factor in medical formulas can be inaccurate and perpetuate health disparities. The previous CKD-EPI 2009 equation included a multiplier for Black individuals.

How often should my eGFR be checked?

The frequency depends on your individual risk factors and overall health. People with diabetes, hypertension, heart disease, or a history of kidney problems may need checks every 6-12 months. Those with normal kidney function and no risk factors might have it checked less frequently, perhaps as part of routine physicals. Your doctor will determine the appropriate schedule for you.

Can a temporarily high creatinine reading affect my long-term prognosis?

A single high creatinine reading due to temporary factors (like dehydration or high meat intake) typically won't affect your long-term prognosis if your kidneys recover. However, persistently elevated creatinine levels that result in a low eGFR over time are indicative of chronic kidney issues and require ongoing management. Your doctor looks at trends rather than isolated results.

What is the role of Cystatin C in eGFR calculation?

Cystatin C is another marker used to estimate GFR. It's produced by all nucleated cells at a relatively constant rate and is less affected by muscle mass, diet, and sex than creatinine. Some newer equations (like CKD-EPI Cystatin C or combined Creatinine-Cystatin C) are available and may offer a more accurate GFR estimate in certain situations, particularly when creatinine-based eGFR is questionable.

Related Tools and Internal Resources

• eGFR Calculator: Use our primary tool to estimate your kidney function.
• Understanding Kidney Health: Learn more about kidney function and common diseases.
• Blood Pressure Tracker: Monitor your blood pressure, a key factor in kidney health.
• Diabetes Management Guide: Discover strategies for controlling blood sugar, vital for preventing kidney damage.
• CKD Stages Chart: Visualize the progression of Chronic Kidney Disease.
• Kidney Disease FAQs: Get answers to common questions about kidney health.