What is PT/INR?

Ouch! You cut yourself. Time to go through the normal routine: apply some pressure, stop the bleeding, and slap on a bandage if you need one. Seems easy enough from the outside. But inside your body, even a little nick from shaving or a scratch from a pet will kick off a series of complex steps in an effort to stop the bleeding.

One of those steps is to send a bunch of proteins, more commonly known as clotting factors, to the injured area. These proteins work together in a very specific way to make a blood clot, which is basically a solid lump of blood that stops up the bleeding and helps the healing process to begin.

That’s how it’s supposed to work. When it doesn’t, you may find that you bleed or bruise easily or that you get clots in your blood vessels when you shouldn’t.

Prothrombin, or factor II, is one of the clotting factors made by the liver. Prothrombin is converted into active thrombin during blood coagulation.

Prothrombin time (PT) is a blood test that measures how long it takes blood to clot. Prothrombin time is an important test because it checks to see if five different blood clotting factors (factors I, II, V, VII, and X) are present and is used to check for bleeding problems. A PT test is also used to check whether medicine to prevent blood clots is working.

A PT test may also be called an INR test. INR (international normalized ratio) stands for a way of standardizing the results of prothrombin time tests, no matter the testing method. It lets your doctor understand results in the same way even when they come from different labs and different test methods. In some labs, only the INR is reported and the PT is not reported.

The prothrombin time is made longer by:

  1. Blood-thinning medicine, such as warfarin
  2. Low levels or absence of blood clotting factors
  3. A change in the activity of any of the clotting factors
  4. Inhibitors that affect the clotting factors
  5. An increase in the use of the clotting factors

An abnormal prothrombin time is often caused by liver disease or injury or by treatment with blood thinners. Your doctor may order a PT/INR test if you have the following symptoms:

  1. Easy bruising
  2. Frequent or heavy nosebleeds
  3. Heavy or prolonged menstrual periods
  4. Blood in the urine
  5. Swollen and painful joints caused by bleeding into your joint spaced

When will I receive my results?

Once completed, you will receive your results within 3-5 business days in your LabFinder portal.

How do I prepare? Do I need to fast?

No preparation or fasting required. Just bring your LabFinder Order and Insurance Card to your appointment.

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This is for educational purposes only. LabFinder does not provide medical advice, diagnosis or treatment. All users should consult with a medical provider in person for any health concerns.
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