Creatinine Clearance (Calculated)

How This Test Works

Your doctor may order this test to evaluate how well your kidneys are working. It involves collecting a sample of your urine over a 24-hour period and a blood sample. The test calculates your creatinine clearance by comparing the amount of creatinine in your urine to the amount in your blood over the same time period. This helps determine how effectively your kidneys are filtering waste products from your bloodstream.

What to Expect Before the Test

No special preparation is needed for this test. You may need to collect your urine sample at home over 24 hours, or it can be done in a clinic. Ensure you drink enough fluids to produce urine throughout the day. If you’re doing a home collection, follow your healthcare provider’s instructions carefully.

What to Expect During the Test

If done in a clinic, a blood sample will be taken from a vein in your arm. For the urine sample, you’ll typically collect all urine produced over a full day. If you’re unsure about timing or collection, ask your healthcare provider for guidance.

Possible Causes for Testing

Doctors may order creatinine clearance tests to diagnose or monitor kidney disease, evaluate kidney function before surgery, check for kidney problems in people with diabetes or high blood pressure, or assess kidney function in people with chronic conditions like heart disease.