The Creatinine to GFR Calculator is a medical tool used to estimate kidney function by converting a patient’s serum creatinine levels into an estimated glomerular filtration rate (eGFR). The GFR is a critical measurement that shows how well the kidneys are filtering waste and excess fluid from the blood.
Doctors, healthcare providers, and patients often use the creatinine to GFR calculation to evaluate kidney health, diagnose chronic kidney disease (CKD), and monitor disease progression. Since direct measurement of GFR is complex, estimated formulas provide a reliable way to assess kidney function using easily obtainable lab values such as creatinine, age, sex, and race.
Creatinine to GFR Calculator
How to Use the Creatinine to GFR Calculator
Using this calculator is simple and requires just a few clinical inputs:
- Enter Serum Creatinine (mg/dL or μmol/L): Input the measured blood creatinine level.
- Select Age: Enter the patient’s age (in years).
- Choose Gender: Male or female, since kidney function varies by sex.
- Choose Ethnicity (if required): Some formulas, such as MDRD or CKD-EPI, include ethnicity adjustments.
- Click Calculate: The tool instantly provides the estimated GFR (eGFR) in mL/min/1.73m².
Formula for Calculating eGFR from Creatinine
Several equations are commonly used to calculate GFR from creatinine. The most widely accepted are:
1. MDRD (Modification of Diet in Renal Disease) Formula:
eGFR = 175 × (Serum Creatinine)^-1.154 × (Age)^-0.203 × (0.742 if female) × (1.212 if Black)
2. CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) Formula:
This formula is more accurate at higher GFR values:
For females:
- If Scr ≤ 0.7 → eGFR = 144 × (Scr / 0.7)^-0.329 × (0.993^Age)
- If Scr > 0.7 → eGFR = 144 × (Scr / 0.7)^-1.209 × (0.993^Age)
For males:
- If Scr ≤ 0.9 → eGFR = 141 × (Scr / 0.9)^-0.411 × (0.993^Age)
- If Scr > 0.9 → eGFR = 141 × (Scr / 0.9)^-1.209 × (0.993^Age)
(Scr = serum creatinine in mg/dL)
Example Calculations
Example 1:
- Serum creatinine = 1.0 mg/dL
- Age = 50 years
- Gender = Male
- Race = Non-Black
Using MDRD formula:
eGFR = 175 × (1.0^-1.154) × (50^-0.203) × (1) = 78 mL/min/1.73m²
Example 2:
- Serum creatinine = 0.8 mg/dL
- Age = 40 years
- Gender = Female
- Race = Black
Using CKD-EPI formula:
eGFR ≈ 98 mL/min/1.73m²
Why eGFR Matters
- Kidney health assessment – Helps detect early kidney damage.
- CKD diagnosis – A GFR < 60 for 3+ months usually indicates chronic kidney disease.
- Treatment monitoring – Evaluates how well medications or lifestyle changes are working.
- Drug dosing – Many medications require adjustment based on kidney function.
Additional Insights
- Normal eGFR is usually 90 or higher.
- eGFR between 60–89 may indicate mild kidney damage.
- eGFR below 60 suggests chronic kidney disease.
- eGFR below 15 often indicates kidney failure, requiring dialysis or transplant.
20 Frequently Asked Questions (FAQs)
Q1. What is GFR?
A: GFR (glomerular filtration rate) measures how much blood the kidneys filter each minute.
Q2. Why is creatinine used to calculate GFR?
A: Creatinine is a waste product filtered by kidneys, making it a reliable marker of kidney function.
Q3. What is a normal creatinine level?
A: Typically, 0.6–1.2 mg/dL in men and 0.5–1.1 mg/dL in women.
Q4. Can GFR be measured directly?
A: Yes, but it requires complex tests with inulin or radioactive tracers, so estimation is more practical.
Q5. What is the difference between MDRD and CKD-EPI equations?
A: CKD-EPI is more accurate for higher GFR values, while MDRD is more commonly used in clinics.
Q6. What does eGFR stand for?
A: Estimated Glomerular Filtration Rate.
Q7. Why does age affect GFR?
A: Kidney function naturally declines with age, even in healthy individuals.
Q8. Why is gender included in the formula?
A: Men generally have higher muscle mass and creatinine production than women.
Q9. How does race affect GFR calculation?
A: Some formulas adjust for race, though recent guidelines are moving away from race-based equations.
Q10. What is considered low GFR?
A: Below 60 mL/min/1.73m² indicates possible chronic kidney disease.
Q11. Can dehydration affect creatinine levels?
A: Yes, dehydration can temporarily raise creatinine levels, lowering eGFR.
Q12. How often should kidney function be tested?
A: At least annually for at-risk individuals (diabetes, hypertension, family history).
Q13. Does diet affect creatinine?
A: High-protein diets can slightly raise creatinine, impacting GFR estimates.
Q14. Is eGFR accurate in children?
A: No, pediatric-specific formulas like the Schwartz equation are used.
Q15. Can muscle mass affect eGFR?
A: Yes, very muscular individuals may appear to have lower eGFR due to higher creatinine production.
Q16. What is the relationship between creatinine and kidney disease?
A: Elevated creatinine often indicates impaired kidney function.
Q17. Can eGFR improve?
A: It can improve with treatment of reversible causes, but chronic decline may not be reversible.
Q18. Is eGFR affected during pregnancy?
A: Yes, kidney function increases in pregnancy, leading to lower creatinine levels.
Q19. Can medications affect creatinine?
A: Yes, some drugs interfere with creatinine secretion, falsely lowering eGFR.
Q20. What should I do if my eGFR is low?
A: Consult a nephrologist for further testing, lifestyle changes, and treatment.