Creatinine Clearance (from Serum)

What Is Creatinine Clearance?

Creatinine clearance is a measure of kidney function that estimates how well your kidneys filter waste products like creatinine from your blood. Unlike a single creatinine blood test, this test uses both your serum creatinine level and your urine output over time to provide a more accurate picture of kidney health. It helps doctors determine how well your kidneys are working to remove waste and maintain fluid balance in your body.

Why Is This Test Done?

Your doctor may order creatinine clearance if they suspect kidney disease, monitor kidney function before or after treatments (like chemotherapy or surgery), or check for kidney problems in people with conditions like diabetes, high blood pressure, or heart disease. It’s also used to guide dosing of medications that are processed by the kidneys.

How Is the Test Performed?

For creatinine clearance, you’ll typically provide a blood sample (serum) and a 24-hour urine collection. The blood test measures creatinine levels in your blood, while the urine test measures how much creatinine is excreted over 24 hours. The results are then used to calculate your clearance rate.

What Do the Results Mean?

Results are usually reported as a clearance rate (e.g., milliliters per minute or milliliters per hour). Lower clearance rates may indicate kidney damage or reduced kidney function, while higher rates suggest normal or improved kidney function. Your doctor will compare your results to your baseline and any known conditions to interpret them accurately.