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 NamesPT; Pro-time
How the test is performedThe 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 testYour 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 feelWhen 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.
Why the test is performedYour doctor may order this test if you have signs of a blood clotting disorder.
When you bleed, the body launches a series of activities that help the blood clot. This is called the coagulation cascade. The PT test looks at special proteins (called coagulation factors) that are involved in this event, and measures their ability to help blood clot.
It measures:
The normal range is 11 to 13.5 seconds. The PT result will be longer in persons who take blood thinners.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results meanWhen any of the blood clotting factors are lacking or not working properly, the PT is prolonged.
Increased PT may be due to:
This test is often done on people who may have bleeding problems. The risks of bleeding and hematoma in these patients are slightly greater than for people without bleeding problems. In general, risks of any blood test may include:
Schafer AI. Approach to the patient with bleeding and thrombosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 178.
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 NamesPT; Pro-time; Anticoagulant-prothrombin time
How the test is performedThe 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 testMake sure your doctor knows about all the medicines you are taking, including over-the-counter medicines, herbs, and supplements. 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 feelWhen 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.
Why the test is performedYour doctor may order this test if you have signs of a blood clotting disorder.
If you are taking a blood thinning medicine called warfarin, your health care provider will check your PT or prothrombin time regularly.
When you bleed, the body launches a series of activities that help the blood clot. This is called the coagulation cascade. The PT test looks at special proteins (called coagulation factors) that are involved in this event, and measures their ability to help blood clot.
Normal ValuesThe normal range for someone who is not taking a blood thinner medication is 11 - 13.5 seconds.
The PT result will be longer in persons who take blood thinners. Ask your doctor what result is right for you.
Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different specimens.
What abnormal results meanWhen any of the blood clotting factors are lacking or not working properly, the PT is prolonged.
A PT result that is too high or too low in someone who is taking warfarin (Coumadin) may be due to:
Increased PT may also be due to:
This test is often done on people who may have bleeding problems. The risks of bleeding and hematoma in these patients are slightly greater than for people without bleeding problems. In general, risks of any blood test may include:
Schafer AI. Approach to the patient with bleeding and thrombosis. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 178.
Schmaier AH. Laboratory evaluation of hemostatic and thrombotic disorders. In: Hoffman R, Benz EJ Jr, Shattil SJ, et al, eds. Hoffman Hematology: Basic Principles and Practice. 5th ed. Philadelphia, Pa: Churchill Livingstone Elsevier; 2008:chap 122.
Reviewed ByReview Date: 02/13/2011
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
The INR has basically replaced the prothrombin time, or PT.
Prothrombin time (PT) primarily measures the activity of clotting factors I (fibrinogen), II (prothrombin), V, VII, and X.
A light blue tube is typically used for a prothrombin time (PT) test.
It decreases synthesis of thromboxane A2 and prostaglandins to increase bleeding time. It does not affect PT or PTT. Prothrombin time unaffected!
pt (prothrombin time)
Prothrombin time (PT) and partial thromboplastin time (PTT) tests are used to evaluate the extrinsic coagulation system
The color top tube used for prothrombin time (PT) is typically light blue. This tube contains sodium citrate as an anticoagulant, which is necessary to prevent blood clotting during PT testing.
Prothrombin time (PT) and partial thromboplastin time (PTT) are tests that are used to evaluate the extrinsic coagulation system.
PT means prothrombin time; 18.3 sounds too slow. Normal is about 9
The test is also known as the pro time or PT test.
prothrombin time is a factor involved in the clotting process. the factors nearly all of which are produced in the liver.
The prothrombin test specifically evaluates the presence of factors VIIa, V, and X, prothrombin, and fibrinogen.