Creatinine Blood Test

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KEY POINTS

• The creatinine blood test is done to see how well your child’s kidneys are filtering waste from your child’s body. This test can help diagnose kidney disease and see how well treatment is working.
• A small amount of blood is taken from a vein in your child’s arm with a needle, or with a heel prick on a baby. The blood is collected in tubes and sent to a lab. This blood test is sometimes done with a 24-hour urine test. It is done either right before your child starts to collect urine or the day your child finishes collecting urine.
• Talk to your child’s healthcare provider about what the test results mean and ask any questions you have.

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What is the creatinine blood test?

This test measures the level of creatinine in the blood. Creatinine is a waste product that is made when another chemical, creatine, is broken down to produce energy for the muscles. This waste product is carried by the blood to the kidneys, where waste is filtered from the body into the urine.

Why is this test done?

This test may be done to see how well your child’s kidneys filter waste from the body. It can help diagnose kidney disease and see how well treatment is working.

How do I prepare for the test?

• Your child’s healthcare provider may ask your child not to eat anything and to drink only water for a while before the test.
• Your child may need to avoid taking certain medicines before the test because they might affect the test result. Tell your child's healthcare provider about all the medicines and supplements your child takes. Ask your child’s provider before stopping any of your child’s regular medicines.
• Talk to your child’s healthcare provider if you have any questions about the test.

How is the test done?

Having this test will take just a few minutes. For babies, the heel may be pricked and a small amount of the blood is taken. For children, a small amount of blood is taken from a vein in your child’s arm with a needle. The blood is collected in tubes and sent to a lab.

This blood test is sometimes done with a 24-hour urine test. It is done either right before your child starts to collect urine or the day your child finishes collecting urine.

Ask your child’s healthcare provider how and when you will get your child’s test results.

What does the test result mean?

Some of the reasons your child’s creatinine blood level may be higher than normal are:

• Your child’s kidneys are not working well.
• Your child has a kidney infection.
• Your child has something blocking the flow of urine such as a kidney stone.
• Your child is dehydrated or has not been drinking enough liquids to replace body fluid lost through blood loss, sweat, or urine.
• Your child has decreased blood flow to the kidneys.
• Your child has muscle damage after a severe injury.
• Your child is taking a medicine that affects your child’s creatinine level.

Your child’s creatinine blood level may be lower than normal if your child has a disease that causes a loss of muscle tissue such as myasthenia gravis or muscular dystrophy. It can also be low if your child does not eat enough protein or has lost a lot of weight.

What if my test result is not normal?

Test results are only one part of a larger picture that takes into account your child’s medical history, physical exam, and current health. Sometimes a test needs to be repeated to check the first result. Talk to your child’s healthcare provider about your child’s result and ask questions such as:

• If your child needs more tests
• What kind of treatment your child may need
• What lifestyle, diet, or other changes you might need to make