The Creatinine Clearance Test (2024)

How does a creatinine clearance test work?

A creatinine clearance test checks samples of your pee and blood for creatinine, a waste product. When your kidney function declines, they don’t filter waste as well. This means it ends up in your blood. This is just one of many tests that healthcare providers use to check kidney function. The key difference in this test is that you collect urine for 24 hours instead of just one time.

Your provider also measures the amount of creatine in your blood using a blood sample. They use these results to come up with your GFR. Your GFR tells your provider how well your kidneys are working.

When is the creatinine clearance test done?

Your healthcare provider may order a creatinine clearance test when they believe results of an eGFR blood test aren’t accurate. Examples includes when people have very little or a lot of muscle mass. A bodybuilder is an example of someone who may have a lot of muscle mass.

Is the creatinine clearance test done at home?

The pee collection part of a creatinine clearance test is done at home and the blood sample part is in a lab or at your provider’s office. You’ll collect all of your pee over 24 hours at home. During this time, you can still participate in your normal daily activities. You just need to stick to a schedule for collecting your urine samples and make sure not to miss any collections (you don’t flush any urine).

The second part of the test involves having your blood drawn. Your provider will give you directions on where to go to for the blood test when you pick up your test materials. Often, you’ll drop off your urine collection when you go to get your blood drawn.

What do I need to do to prepare for the creatinine clearance test?

Before the creatinine clearance test, your healthcare provider will tell you what you may need to do to prepare.

Your provider will give you a container to pee in and tell you how to store it over the 24-hour period when you’re collecting it. It’s important to follow the instructions your provider gives you. Make sure you collect urine throughout the test. If you skip a few times or don’t follow the instructions, you may need to repeat the test.

Some medications could affect the test’s accuracy, so you might need to temporarily stop taking them. Only stop taking medications if your healthcare provider tells you to. Make sure to let your provider know about any medication you’re taking and that there’s a complete list of all your medications in your medical record.

Do I need to fast before the creatinine clearance test?

In general, you can eat normally before and during the creatinine clearance test. However, your provider may tell you not to eat overnight. They may also ask you not to eat meat before the test. This could change the results because there’s higher levels of creatine in meat, which would cause your body to have higher levels of creatinine during the test.

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What happens during the creatinine clearance test?

You’ll do the creatinine clearance test over 24 hours. During this time, you’ll collect your urine each time you pee. This will give your healthcare provider a good idea of your creatinine levels throughout the entire day.

Make sure to follow the directions from your healthcare provider closely. These instructions will include details about how to store your urine sample and where you’ll take it when the test is over.

After 24 hours of collecting your pee, you’ll need to have your blood drawn. This blood sample checks for creatinine in your bloodstream. This is called serum creatinine. Your provider will use a mathematical formula that determines your creatinine clearance. This rate tells your provider just how well your kidneys are filtering waste products out of your bloodstream.

What happens if I forget to collect one urine sample during collection?

It’s very important to collect urine samples throughout the entire day for the creatinine clearance test to be accurate. If you skip one urine collection, it could affect the test results. Call your healthcare provider’s office if you miss a collection to see if you should continue the test or stop and start over the next day.

Will I feel any pain during the creatinine clearance test?

The creatinine clearance test is generally painless. The first part of the test involves normal urination over a 24-hour period of time. You might experience some discomfort from the needle when you have your blood drawn. This is a necessary part of the test and happens quickly.

What should I expect after a creatinine clearance test?

Once you complete the test, you only need to wait to hear from your healthcare provider about next steps. It may take a few days to hear your results.