Creatinine Tests: About These Tests

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What are they?

Creatinine tests measure the level of the waste product creatinine (say "kree-AT-uh-neen") in your blood and urine. These tests show how well your kidneys are working.

When the kidneys are not working well, they cannot filter creatinine from the blood. This causes the level of creatinine in the blood to go up and the creatinine clearance-the test that measures how well your kidneys remove creatinine-to go down.

Why are these tests done?

A blood creatinine level or a creatinine clearance test is done to:

  • See if your kidneys are working normally or if a medicine is affecting your kidneys.
  • See if your kidney disease is staying the same or getting better or worse.

How can you prepare for the tests?

You may be asked to:

  • Not do any strenuous exercise for 2 days (48 hours) before having the tests.
  • Not eat more than 225 grams of meat, especially beef, or other protein for 24 hours before the blood creatinine test and during the creatinine clearance urine test.
  • Drink plenty of fluids if you are asked to collect your urine for 24 hours. But do not drink coffee or tea. These are diuretics that cause your body to pass more urine than normal.

Tell your doctor about all the non-prescription and prescription medicines and natural health products you take. Some medicines and natural health products can affect the results of these tests.

What happens before the tests?

If you are asked to collect urine, your doctor will give you a large container that holds about 4 litres. You will use the container to collect your urine for 24 hours.

What happens during the tests?

For the urine tests

You collect your urine for 24 hours.

  • You start collecting your urine in the morning. When you first get up, empty your bladder, but do not save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
  • For the next 24 hours, collect all your urine. Urinate into a small, clean container, and then pour the urine into the large container. Do not touch the inside of the container with your fingers.
  • Keep the collected urine in the refrigerator for the 24 hours. Empty your bladder for the final time at or just before the end of the 24-hour period. Add this urine to the large container, record the time, and bring the container to the lab or doctor's office.

For the blood test

A health professional takes a sample of your blood.

How long do the tests take?

  • The urine test will take 24 hours.
  • The blood test will take a few minutes.

What happens after the tests?

  • After the blood test, you will be able to go home right away.
  • You can go back to your usual activities right away.

When should you call for help?

Watch closely for changes in your health, and be sure to contact your doctor or nurse call line if you have any problems.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

Go to https://www.healthwise.net/patientEd

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