Creatinine Clearance (from Serum)

Why This Test Matters

Creatinine clearance is a critical test for evaluating kidney function because it reflects how effectively your kidneys remove waste products from your blood. Unlike some kidney function tests that measure blood levels of waste, creatinine clearance directly assesses the kidneys' ability to filter waste based on urine output and blood levels.

What to Expect Before the Test

No special preparation is needed for this test. You may have a blood draw (serum sample) and a urine sample collected over a 24-hour period. If your doctor requests a 24-hour urine sample, they may provide instructions to collect all urine for a full day, including overnight. Drink plenty of fluids unless advised otherwise.

How the Test Works

Creatinine clearance is calculated by measuring creatinine levels in both your blood (serum) and urine over a 24-hour period. The test uses the urine volume and creatinine concentration to estimate how much blood your kidneys filter each minute. This process helps determine kidney function and blood flow.

Possible Results and Interpretation

Results are typically reported as a clearance rate (e.g., milliliters per minute or milliliters per hour). Lower than expected clearance may indicate kidney damage or disease, while higher values might suggest overhydration or other conditions affecting urine output. Your healthcare provider will interpret results in relation to your overall health and medical history.