Urine Creatinine 24-Hour Excretion Rate

What This Test Measures

Creatinine is a waste product made by your muscles during normal activity. Your kidneys filter it out of your blood and into your urine. This test measures the total amount of creatinine passed in your urine over 24 hours and reports it as a rate (for example, an amount per unit of time), giving a picture of how well your kidneys are removing this waste.

How the Sample Is Collected

You will collect all of your urine for a full 24-hour period in a special container provided by your lab. The collection usually starts after you empty your bladder in the morning and discards that first sample, then continues until the same time the next day. It is important to keep the container refrigerated and to follow your lab's instructions carefully so the collection is complete.

Why Completeness Matters

A 24-hour urine test only gives reliable results if every drop of urine is collected during the entire period. The creatinine excretion rate is often used to check whether a collection is complete. If the amount collected is much lower or higher than expected, your doctor may ask you to repeat the collection.

What to Expect

Collecting urine for 24 hours can be inconvenient, but the test itself is painless. You may need to adjust your routine to stay near a restroom and to store the container properly. Bring the full container to the lab as instructed.