ProTime INR is short for prothrombin time (PT) and international normalized ratio (INR). Prothrombin time is a test that helps your healthcare provider see if your blood clots properly. INR is a calculation based on that test. It compares your blood clotting time to a typical range of time for clotting. This information can help your healthcare provider make sure you are taking the right dose of a blood-thinning medication.

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Why is a prothrombin time test important?

Some people have medical conditions that cause their blood to not clot properly. Their blood might clot too quickly or too slowly. They might not have enough of one of several particular components called coagulation factors to make the process happen correctly.

Prothrombin is one of these clotting factors. It’s a protein made by the liver. People who don’t have enough of this protein might experience excessive bleeding. If they have too much, it can lead to excessive clotting. The ProTime INR test can determine if they have too much or too little prothrombin.

Other conditions that can cause blood to clot too slowly include:

  • Vitamin K deficiency
  • Certain liver conditions
  • Low levels of other coagulation factors
  • Blood-thinning medications

What should you expect with a prothrombin test?

A healthcare provider will draw a sample of blood from your arm. The blood sample will be sent to a lab.

How does the test work?

A prothrombin time test measures the number of seconds it takes for your blood to clot. A lab technician adds a substance called a reagent to a sample of your blood. The technician then compares the time it takes for your blood to clot to the standard time it should take for blood to clot. This ratio is called the INR. If your ratio is high, your blood clots more slowly. You may be at risk for excessive bleeding. A lower ratio means your blood clots too quickly. Depending on your results, your healthcare provider may recommend taking a blood-thinning medication.

People who take blood thinners for long periods of time may be able to test their own blood at home with special kits.

If you take a blood thinner and have concerns about bleeding, contact a healthcare provider. Visit your nearest CareNow® urgent care clinic for your healthcare needs.

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