• Home

Home > Medical Reference > Encyclopedia (English)

Toggle: English / Spanish

Prothrombin time (PT)

• Overview
• Risks
• Results

Definition:

Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot.

See also: Partial thromboplastin time (PTT)

Alternative Names:

PT; Pro-time

How the test is performed:

The health care provider uses a needle to take blood from one of your veins. The blood collects into an airtight container. You may be given a bandage to stop any bleeding. If you are taking a medicine called heparin, you will be watched for signs of bleeding.

The laboratory specialist will add chemicals to the blood sample and see how long it takes for the plasma to clot.

How to prepare for the test:

Your doctor may tell you to stop taking certain drugs before the test. For example, blood thinners can affect the results of this test.

Do not stop taking any medicine without first talking to your doctor.

How the test will feel:

When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.

Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.

Why the test is performed:

The PT is a broad screening test for many types of bleeding disorders. Your doctor may order this test if you have signs of a blood clotting disorder.

References:

Ferri FF. Ferri’s Clinical Advisor: Instant Diagnosis and Treatment. 2005 ed. St. Louis, Mo: Mosby; 2005:1365.

Hoffman R, Benz EJ, Shattil SS, et al. Hematology: Basic Principles and Practice . 4th ed. Orlando, Fl: Churchill Livingstone; 2005:2004-2005.

• Review Date: 3/9/2007
• Reviewed By: Mark Levin, MD, Hematologist and Oncologist, Newark, NJ. Review provided by VeriMed Healthcare Network.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is the first of its kind, requiring compliance with 53 standards of quality and accountability, verified by independent audit. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial process . A.D.A.M. is also a founding member of Hi-Ethics (www.hiethics.com) and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).

The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2007 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.