Creatinine Clearance (24-hour urine collection)

Why This Test Is Done

Your doctor may order this test if they suspect kidney disease, need to monitor kidney function before or after treatment, or want to check if your kidneys are working properly after an injury or illness. It’s also used to evaluate kidney function in people with high blood pressure, diabetes, or other conditions that can affect the kidneys.

How the Test Is Done

You’ll collect all urine for a full 24-hour period in a special container. The test measures creatinine, a waste product from muscle metabolism, in your urine to estimate how well your kidneys are filtering it from your blood.

What to Expect Before the Test

No special preparation is needed, but you should drink enough fluids to produce about 600–800 mL (about 2–3 cups) of urine per day. Avoid using certain medications that may affect kidney function unless your doctor advises otherwise.

What to Expect During the Test

You’ll collect urine in a container every time you urinate, including first thing in the morning. At the end of 24 hours, your sample will be tested in a lab to measure creatinine levels.