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PT

Also known as: Prothrombin Time; Pro Time
Formal name: Prothrombin Time
Related tests: Activated Clotting Time (ACT), Activated Partial Thromboplastin Time (aPTT or PTT), Prothrombin Consumption Time (PCT), Fibrinogen, Coagulation Factors

Common Questions

1.  Can I do this test at home?

Yes, although it may be harder to guarantee the accuracy of tests performed at home. Ask your doctor whether home testing is appropriate for you.

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2.  Should I have it done at the same time of day?

Only in the induction period, when a "loading" dose is frequently given and correctly timed INRs are important for predicting the long-term "maintenance" dose. You should ideally take your anti-coagulant tablets in the evening however. This allows your doctor to modify your dose up or down on the same day as your INR test.

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3.  My PT/INR results vary sometimes, yet my doctor doesn’t change my prescription. Why?

The use of any of the drugs mentioned above can alter your results, as can the use of diuretics and antihistamines and the onset of illness or allergies. Certain foods, such as beef and pork liver, green tea, broccoli, chickpeas, kale, turnip greens, and soybean products contain large amounts of vitamin K and can alter PT results. The blood collection technique and the difficulty in obtaining the blood sample can also affect test results.

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