Prothrombin, or factor II, is one of the clotting factors made by the liver. Vitamin K is needed to make prothrombin and other clotting factors. The prothrombin time is made longer by:. An abnormal prothrombin time is often caused by liver disease or injury or by treatment with blood thinners.
The U. If you need a PT test frequently and for a long time, you may want to ask your doctor if this home test is an option for you.
In some cases, the health professional will take a sample of blood from your fingertip instead of your vein. For a finger stick blood test, the health professional will clean your hand, use a lancet to puncture the skin, and place a small tube on the puncture site to collect your blood. When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site. Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. That screening — known as the model for end-stage liver disease MELD — is a scoring system for assessing the severity of chronic liver disease.
If your doctor suspects you have other health issues, such as liver problems or a bleeding disorder, you might need additional testing to confirm your condition.
A prothrombin time test is similar to any other blood test. You might experience soreness or minor bruising at the site in the arm where your blood is drawn. Obtaining the blood sample for prothrombin time testing usually takes just a few minutes, like any other blood test.
Your blood might 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. In some anticoagulation clinics, a nurse will take a sample of your blood with a finger stick, and give you the test result within minutes, while you are still in the exam room. 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.
The average time range for blood to clot is about 10 to 13 seconds. A number higher than that range means it takes blood longer than usual to clot. You can also read more about blood tests in general.
Visit our Guide to blood testing to learn more about blood tests in general with information such as:. Learn more here about the development and quality assurance of healthdirect content. Describes how the prothrombin time PT test is used, why the PT test is done, and what the results might mean. Read more on HealthEngine website. Description of factors involved in coagulation of the blood, factors measured in the investigation of clotting disorders.
The international normalised ratio INR is a laboratory measurement used to determine the effects of oral anticoagulants such as warfarin on the body's blood clotting. Hypercoagulable disorders are a number of different conditions that lead to a predisposition to form blood clots. Explains how fibrinogen is used; when fibrinogen is used; what the results of fibrinogen might mean.
Find out what the key considerations are when prescribing these drugs. Includes CPD activity for pharmacists. Read more on Australian Prescriber website. Healthdirect Australia is not responsible for the content and advertising on the external website you are now entering. There is a total of 5 error s on this form, details are below. Laboratory testing Testing using a portable device Health facility monitoring with a portable device Home monitoring with a portable device Self-testing with a portable device Introduction to blood clotting Coagulation or blood clotting is a protective mechanism of the body against bleeding.
For more information, see Blood Function and Composition. For more information, see Anticoagulants. What is the INR? Regular monitoring is important with a drug such as warfarin because: There is a very small difference between the lowest dose that gives a good effect and the highest dose before side effects which may be serious are experienced; The doses used by different individuals to achieve the same effect can be highly variable; Several drugs interact with the medication to either increase or decrease its effectiveness; and What a person eats can also affect the action of warfarin and either increase or decrease its effectiveness.
Therefore, you should consult your doctor if you: Have a sudden change of diet leafy greens in particular ; Are taking diet supplementation; Are unwell; or Are taking other medications, including over-the-counter medications. Common medications that interfere with warfarin include: Many antibiotics ; Some heart medications, such as amiodarone e. Aratac , Cardinorm , diltiazem e. Cardizem , Diltahexal and propranolol e.
Deralin , Inderal ; Some anti- cholesterol medications, such as simvastatin e. Lipex , Zocor ; Some pain relievers and anti-inflammatories, such as celecoxib Celebrex and tramadol e. Tramal , Zydol ; Some antidepressants , such as citalopram e. Cipramil and sertraline Zoloft ; and Some antiepileptics , such as carbamazepine e. Laboratory testing Laboratory blood testing is the traditional practice in Australia. Testing using a portable device Portable devices, introduced in the s, allow you, your doctor or another health practitioner e.
Health facility monitoring with a portable device If the device is used for monitoring in a health facility, a health practitioner often a nurse conducts the blood test and records the result on your behalf.
Home monitoring with a portable device When a portable device is used for home monitoring, you usually conduct the test yourself. Self-testing with a portable device If you self-test, there are two options available: Self-monitoring: which involves your testing your INR at home, and then phoning a clinic with the result and to find if there is a need to adjust the dose and if so what the dose adjustment is; or Self-management: which involves you testing your INR at home, and adjusting your oral anticoagulant dose based on the result obtained, according to a pre-determined dose INR schedule.
More information For more information on coagulation, including information on anticoagulants, blood coagulation tests and test devices, see Blood Clotting and Monitoring. References Tripodi A. Prothrombin time international normalized ratio monitoring by self-testing. Curr Opin Hematol. A critical evaluation of the prothrombin time for monitoring oral anticoagulant therapy.
Pathophysiol Haemost Thromb. Self-monitoring and self-management of oral anticoagulation. Cochrane Database Syst Rev. Antithrombotic drugs: Part I.
Optimal oral anticoagulant therapy in patients with mechanical heart valves. N Engl J Med. An analysis of the lowest effective intensity of prophylactic anticoagulation for patients with nonrheumatic atrial fibrillation. Comparison of low-intensity warfarin therapy with conventional-intensity warfarin therapy for long-term prevention of recurrent venous thromboembolism. Optimal frequency of patient monitoring and intensity of oral anticoagulation therapy in valvular heart disease.
J Thromb Thrombolysis.
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