GFR Calculator
Estimate kidney function using the CKD-EPI formula. A reference tool for runners who have had creatinine blood tests and want to understand their kidney health.
Reference tool only
This calculator is for educational reference. GFR estimates should always be interpreted by a qualified healthcare professional alongside your full medical history and other test results.
Support your health and fitness
Staying hydrated is crucial for kidney health and running performance. These products help.
Precision Hydration
Electrolyte tablets tailored to your sweat rate. Proper hydration supports kidney function and performance.
View on AmazonHydration Vest
Carry enough water for longer runs. Essential for maintaining proper hydration during training.
View on AmazonHow the GFR Calculator works
GFR is estimated from serum creatinine, age, and sex using the CKD-EPI 2021 equation - the most validated formula for general populations. Strenuous running can temporarily elevate creatinine, so GFR estimates should be taken from resting blood samples.
Frequently asked questions
Does running affect kidney function?
Intense or very long endurance runs can temporarily elevate creatinine (from muscle breakdown) and reduce GFR. This usually returns to baseline within 24–48 hours. Chronic kidney disease in runners is rare - running is protective of kidney health over the long term.