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PT and INR Blood Test (Bleeding Test)

What is the PT and INR test?

The PT and INR blood test measures the time it takes your child’s blood to form a clot. Other names for the PT test are prothrombin time and pro time. INR stands for international normalized ratio.

Why is this test done?

The PT/INR test is usually done when your child is taking a blood thinner (anticoagulant) medicine, such as warfarin (Coumadin), to prevent blood clots. Clots can block blood vessels and possibly cause a heart attack or stroke. This test measures the effect of the anticoagulant. If the dosage is too high, your child may bleed too easily and if it’s too low, your child’s blood may clot too easily. The test helps your child’s healthcare provider find the right dosage of medicine.

The PT test may also be done to diagnose a bleeding disorder if your child has abnormal bleeding or clotting.

How do I prepare my child for this test?

  • Your child may need to avoid taking certain medicines before the test because they might affect the test result. Make sure your child’s healthcare provider knows about any medicines, herbs, or supplements that your child is taking. 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 young babies, the heel is pricked and a small amount of the blood is taken. For older 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.

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

What does the test result mean?

A PT/INR value higher than normal means your child’s blood is taking longer than normal to form a clot. If your child is taking a blood thinner, it means that the medicine is working.

If your child is not taking a blood thinner and your child’s values are higher than normal, your child may:

  • Have liver disease
  • Need more vitamin K (vitamin K is needed to help the blood clot)
  • Have an inherited blood disorder such as hemophilia or von Willebrand disease
  • Have had a lot of heavy bleeding or serious infection recently

What if my child’s 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 the results and ask questions, such as:

  • If your child needs more tests
  • What kind of treatment your child might need
  • What lifestyle, diet, or other changes your child might need to make
Developed by RelayHealth.
Pediatric Advisor 2015.3 published by RelayHealth.
Last modified: 2014-03-10
Last reviewed: 2013-10-10
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.
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