Prothrombin Time (PT) with INR Most Popular

The Prothrombin Time (PT) with INR test contains 1 test with 2 biomarkers.

Description: A Prothrombin Time test will measure the speed of which your blood clots. This test can be used to detect a bleeding or clotting disorder or to determine in your blood is clotting too fast or too slow.

Also Known As: Pro Time with INR Test, Prothrombin Time and International Normalized Ratio test, Prothrombin Time PT with INR Test, Prothrombin Time with INR Test, Prothrombin with INR, Protime with INR, PT Test

Collection Method: Blood draw

Specimen Type: Whole Blood

Test Preparation: No preparation required

Average Processing Time: 1 to 2 days

When is a Prothrombin Time with INR test ordered?

When a person takes the anticoagulant medicine warfarin, a PT and INR are ordered on a regular basis to confirm that the prescription is working effectively and that the PT/INR is adequately extended. A doctor will prescribe them frequently enough to ensure that the treatment is having the desired effect, namely, boosting the person's clotting time to a therapeutic level while minimizing the danger of excessive bleeding or bruising.

When a person who isn't taking anticoagulants exhibits signs or symptoms of excessive bleeding or clotting, a PT may be ordered when they are experiencing:

  • Bleeding that isn't explained or bruises that isn't easy to get rid of
  • Nosebleeds
  • Gums that are bleeding
  • A blood clot in an artery or vein
  • Disseminated intravascular coagulation
  • A persistent disorder that affects hemostasis, such as severe liver disease

PT and PTT may be prescribed prior to surgery when there is a high risk of blood loss associated with the procedure and/or when the patient has a clinical history of bleeding, such as frequent or severe nosebleeds and easy bruising, which may indicate the presence of a bleeding problem.

What does a Prothrombin Time with INR blood test check for?

The prothrombin time is a test that determines a person's capacity to make blood clots properly. The international normalized ratio, or INR, is a calculation based on the results of a PT that is used to track people who are taking the blood thinner warfarin.

After chemicals are added to a person's blood sample, a PT measures how long it takes for a clot to develop. The PT is frequently used with a partial thromboplastin time to measure the number and function of proteins known as coagulation factors, which are essential for optimal blood clot formation.

When an injury develops in the body and bleeding ensues, the clotting process known as hemostasis begins. This process is aided by a series of chemical events known as the coagulation cascade, in which coagulation or "clotting" components are activated one by one, leading to the development of a clot. In order for normal clotting to occur, each coagulation factor must be present in appropriate quantities and operate effectively. Excessive bleeding can result from too little, while excessive clotting can result from too much.

There are two "pathways" that can trigger clotting in a test tube during a laboratory test, the extrinsic and intrinsic pathways. Both of these pathways subsequently converge to finish the clotting process. The PT test assesses how well all coagulation factors in the extrinsic and common routes of the coagulation cascade cooperate. Factors I, II, V, VII, and X are included. The PTT test examines the protein factors XII, XI, IX, VIII, X, V, II, and I, as well as prekallikrein and high molecular weight kininogen, which are all part of the intrinsic and common pathways. The PT and PTT examine the overall ability to generate a clot in a fair period of time, and the test results will be delayed if any of these elements are insufficient in quantity or are not operating effectively.

The PT test is normally done in seconds and the results are compared to a normal range that represents PT levels in healthy people. Because the reagents used to conduct the PT test vary from one laboratory to the next and even within the same laboratory over time, the normal ranges will change. The Internationalized Normalized Ratio, which is computed based on the PT test result, was developed and recommended for use by a World Health Organization committee to standardize results across various laboratories in the United States and around the globe for people taking the anticoagulant warfarin.

The INR is a formula that accounts for variations in PT reagents and enables for comparison of findings from different laboratories. When a PT test is performed, most laboratories report both PT and INR readings. However, the INR should only be used by people who are taking the blood thinner warfarin.

Lab tests often ordered with a Prothrombin Time with INR test:

  • Partial Thromboplastin Time
  • Fibrinogen Activity
  • Platelet Count
  • Complete Blood Count (CBC)
  • Coagulation Factors
  • Warfarin Sensitivity testing

Conditions where a Prothrombin Time with INR test is recommended:

  • Bleeding Disorders
  • Excessive Clotting Disorders
  • Vitamin K Deficiency
  • Liver Disease
  • DIC

How does my health care provider use a Prothrombin Time with INR test?

The prothrombin time is used to diagnose the origin of unexplained bleeding or abnormal blood clots, generally in conjunction with a partial thromboplastin time. The international normalized ratio is a calculation based on the results of a PT that is used to monitor people on the blood thinner warfarin.

Coagulation factors are proteins that are involved in the body's process of forming blood clots to assist stop bleeding. When an injury occurs and bleeding begins, coagulation factors are triggered in a series of events that finally assist in the formation of a clot. In order for normal clotting to occur, each coagulation factor must be present in appropriate quantities and operate effectively. Excessive bleeding can result from too little, while excessive clotting can result from too much.

The PT and INR are used to monitor the anticoagulant warfarin's efficacy. This medication influences the coagulation cascade's function and aids in the prevention of blood clots. It is given to those who have a history of recurrent abnormal blood clotting on a long-term basis. Warfarin therapy's purpose is to strike a balance between preventing blood clots and causing excessive bleeding. This equilibrium must be carefully monitored. The INR can be used to change a person's medication dosage in order to get their PT into the ideal range for them and their condition.

What do my PT and INR test results mean?

Most laboratories report PT findings that have been corrected to the INR for persons taking warfarin. For basic "blood-thinning" needs, these persons should have an INR of 2.0 to 3.0. Some people with a high risk of blood clot require a higher INR, about 2.5 to 3.5.

The outcome of a PT test is determined by the method utilized, with results measured in seconds and compared to a normal range defined and maintained by the laboratory that administers the test. This normal range is based on the average value of healthy persons in the area, and it will differ somewhat from test to lab. Someone who isn't on warfarin would compare their PT test result to the usual range provided by the laboratory that conducted the test.

A prolonged PT indicates that the blood is taking an excessive amount of time to clot. This can be caused by liver illness, vitamin K inadequacy, or a coagulation factor shortage, among other things. The PT result is frequently combined with the PTT result to determine what condition is present.

We advise having your results reviewed by a licensed medical healthcare professional for proper interpretation of your results.

The following is a list of what is included in the item above. Click the test(s) below to view what biomarkers are measured along with an explanation of what the biomarker is measuring.

Also known as: Pro Time with INR, Prothrombin Time and International Normalized Ratio, Prothrombin Time PT with INR, Prothrombin Time with INR, Protime with INR, PT


International normalized ratio (INR) - To check how well the blood-thinning medication (anticoagulant) warfarin (COUMADIN®) is working to prevent blood clots; to help detect and diagnose a bleeding disorder. Internationalized Normalized Ratio (INR) with the PT test for people who are receiving the anticoagulant warfarin (COUMADIN®).


Prothrombin time (PT) is a blood test that measures the time it takes for the liquid portion (plasma) of your blood to clot.
*Process times are an estimate and are not guaranteed. The lab may need additional time due to weather, holidays, confirmation/repeat testing, or equipment maintenance.

Customer Reviews