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Creatinine Tests: About Your Child's Test

Location of the kidneys, with detail of how the kidneys filter waste from the blood

What are they?

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

Why are these tests done?

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

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

How can you prepare for the tests?

Your child may be asked to:

  • Not do any hard exercise for 2 days (48 hours) before the test.
  • Not eat more than 225 grams (8 oz) 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 your child is asked to collect his or her urine for 24 hours. But don't let your child drink coffee or tea. These cause your child's body to pass more urine than normal.

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

What happens during the tests?

For the urine tests

Your child's urine is collected for 24 hours in the large container the doctor gave you.

  • Urine collection starts in the morning. When your child first gets up, your child should empty his or her bladder. But don't save this urine. Write down the time that your child urinated to mark the start of the 24-hour collection period.
  • For the next 24 hours, collect all your child's urine. Have your child urinate into a small, clean container. 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. Have your child empty his or her 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 child's 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, your child will be able to go home right away.
  • Your child can go back to his or her usual activities right away.

Follow-up care is a key part of your child's treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse call line if your child is having problems. Ask your doctor when you can expect to have your child's test results.

Where can you learn more?

Go to

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Care instructions adapted under license by your healthcare professional. If you have questions about a medical condition or this instruction, always ask your healthcare professional. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.