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By Mayo Clinic staff
During the test
Prothrombin time testing is done using a blood sample. Usually, the blood is drawn through a small needle inserted into a vein in the bend of your arm. You'll be asked to roll up your shirt sleeve if you're wearing long sleeves. The person drawing the blood might tie a band around your upper arm and ask you to make a fist. This causes your vein to stick out more, making it easier to insert the needle. The needle is attached to a small tube, in which your blood is collected. All of this usually takes just a few minutes.
You may feel a quick pain as the needle is inserted and experience some short-term discomfort at the site after the needle is removed.
After the test
Once the needle is removed, you'll be given a piece of gauze and a bandage to cover the area where the needle was inserted. You'll be asked to gently apply pressure to the area for a minute or so, to help stop any bleeding.
Your blood will be sent to a laboratory for analysis. If the laboratory analysis is done on-site, you could have your test results within hours. If your doctor sends your blood to an off-site laboratory, it may take several days to receive the results.
Home testing
Home testing kits are available for people who have to take blood thinners for long periods and who have been trained in taking blood samples and testing them.
- PT and INR. Lab Tests Online. http://www.labtestsonline.org/understanding/analytes/pt/glance.html#. Accessed Oct. 3, 2012.
- Prothrombin time. Mayo Medical Laboratories. http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/9236. Accessed Oct. 3, 2012.
- Feldman M, et al. Sleisenger & Fordtran's Gastrointestinal and Liver Disease: Pathophysiology, Diagnosis, Management. 9th ed. Philadelphia, Pa.: Saunders Elsevier; 2010. http://www.mdconsult.com/books/about.do?eid=4-u1.0-B978-1-4160-6189-2..X0001-7--TOP&isbn=978-1-4160-6189-2&about=true&uniqId=229935664-2192. Accessed Oct. 3, 2012.
- Friedman LS. Tests of the liver's biosynthetic capacity (e.g., albumin, coagulation factors, prothrombin time). http://www.uptodate.com/index. Accessed Oct. 3, 2012.
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