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PT Corona Pathology 1 - PT

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PT stands for Prothrombin Time. Prothrombin Time is a blood test that measures how long it takes a person’s blood to clot. The test is a simple blood test.

  • It helps identify excessive clotting disorders or bleeding disorders.
  • Prothrombin Time is also used to verify that blood clotting medicines are working properly.



A PT test is sometimes referred to as an international normalized ratio test (INR). INR is a way to make sure the results of the test are universally understood by standardizing them. This method allows a doctor to interpret results in the same fashion regardless of different laboratory or test procedures. Sometimes only the international normalized ratio is reported and the prothrombin time is not.

Why Have a PT Done?

A doctor might order a Prothrombin Time for a patient to check the:

  • Effects of Warfarin (blood thinning medicine)
  • Dose of Warfarin (blood thinning medicine)
  • Vitamin K levels
  • Blood clotting factors (family history of clotting disorders)
  • Liver function

Prothrombin Time is frequently tested before surgery to make sure the surgery is a safe option. Another reason a doctor orders a PT test is to make sure the body is not using clotting factors too quickly. If the body uses the factors too quickly, a patient may not stop bleeding which is called disseminated intravascular coagulation (DIC).

PT Corona Pathology 2 - PT

What Affects the Results of the PT?

It is important to postpone the exam if any of the following has occurred within 24 to 48 hours before the test:

  • Severed diarrhea or vomiting
  • Taking certain medicines (aspirin, barbiturates, birth control pills)
  • Eating foods high in Vitamin K (broccoli, soybean, kale, or chickpeas)
  • Consuming an excessive amount of alcohol
  • Taking natural remedies or herbal supplements

These situations can affect the results of the Prothrombin Time, and the test may not be accurate.

Risks Involved with the Prothrombin Time Test

The PT test is a simple blood test, so the risks are minimal. However, a patient might experience bruising around the area. This bruising can be diminished if pressure is applied directly after blood has been drawn. If the patient has a bleeding disorder, he or she may have continuous bleeding from the site. If this happens, it is important to notify the doctor immediately.


The Prothrombin Time is the amount of time it takes an individual’s blood to clot. If the blood clots in 11 to 13.5 seconds, it is within the standard range. The international normalized ratio is a calculation based on results of a PT for doctors to have a universal understanding of the results. The average range for the international normalized ratio is 0.8 to 1.1.

For example, if the international normalized ratio number is above 1.1, the blood is clotting too slowly. This result could mean a patient has a bleeding disorder, liver disease, Vitamin K deficiency, or disseminated intravascular coagulation. Other tests may be needed to diagnose any actual illness.