Creatinine Clearance (24-hour urine collection)

Why This Test Is Done

Your doctor may order this test if you have symptoms like swelling, frequent urination, fatigue, or if you have a history of kidney problems, diabetes, high blood pressure, or other conditions that can affect kidney function. It may also be used to monitor kidney health before or after treatments like chemotherapy or certain medications.

How the Test Works

You’ll collect all your urine over a full 24-hour period in a special container. Blood is drawn at the start and end of the collection period to measure creatinine levels in your blood. The test compares the creatinine levels in your urine and blood to estimate how well your kidneys are filtering waste.

Sample Collection Process

On the day of your test, you’ll need to urinate completely into a toilet, then start collecting all urine for the next 24 hours—including during the night—into a clean container. Keep the container in a cool place. On the following day, you’ll urinate into the toilet first, then discard that urine. After that, you’ll finish collecting all urine for the final 24 hours. Bring all collected urine to your doctor’s office or lab with your blood samples.

What to Expect Before the Test

No special preparation is needed, but you should drink enough water to produce clear urine. Avoid taking certain medications that may affect kidney function without consulting your doctor. If you have a kidney-related condition or are pregnant, let your healthcare provider know.