PT INR Normal Values


PT INR normal values are important figures that help doctors determine the ability of a person’s blood to clot. The standard values of PT INR may vary from lab to lab, and so it is very important to have the PT INR results interpreted by qualified physician. Doctors can determine the occurrence of improper and dangerous blood clotting by comparing the PT INR test results to the normal values set by the laboratory.

Those who fail to achieve the ideal PT INR normal values will undergo further testing to rule out the underlying cause. Resolving abnormal PT INR values is very important to prevent life-threatening situations.

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What is PT INR?

PT INR normal values slightly differ between clinical laboratories. PT refers to prothrombin time, a type of blood test that measures a person’s blood clotting time. There are various ways to test PT and because of the differences of testing methods used by laboratories, INR or international normalized ratio is used to standardize the PT test results.

When is PT INR test done?

PT INR normal values are helpful guidelines when interpreting the PT INR test result. The test is primarily done to patients who are receiving anticoagulant therapy. Anticoagulants are utilized to prevent inappropriate and dangerous blood clotting which may lead to heart attacks, strokes, cerebrovascular accidents and deep vein thrombosis. People who receive artificial heart valves also receive anticoagulant therapy. PT INR test is also done to those who exhibit bleeding disorder symptoms which is characterized by bleeding gums, nosebleeds, bruising, bloody stool and urine, heavy menstrual flow, chronic anemia, vision loss and arthritic-type symptoms. The test is also conducted when the patient is schedules to go through a surgical procedure to determine the blood clotting ability of the patient.

How important is it to maintain PT INR at normal levels?

Maintaining PT INR normal values is extremely important to avoid the dreadful and serious complications that may occur due to abnormal PT INR levels which could result into dangerous blood clotting or excessive bleeding. Stroke is the number one cause of disability in adults and ranked as the third cause of high mortality among Americans. The finest way patients can determine their PT INR levels is to have it checked by a laboratory or through commercially available self-testing kits. The frequency of PT INR test differs with every individual, though most often it is done once in every 4 or 6 weeks.

How much should normal PT INR values be?

The PT INR normal values differ for every individual and depending on a number of factors including medical conditions that result in taking anticoagulants. Normal PT INR values also differ between those who take anticoagulants and those who do not.

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  • Normal PT range – 10 to 13.5 seconds
  • Normal PT INR range for people taking anticoagulants – 2.0 to 4.0
  • Normal PT INR range for people not taking anticoagulants – 0.8 to 1.2

The doctor will be the one to determine the ideal PT INR value for his or her patient.

What do abnormal PT INR values indicate?

People who fall short in reaching PT INR normal values should be wary. This is because an abnormal PT INR value is a strong indication that there is a higher possibility for stroke or bleeding to occur. If the PT INR values are found on the higher end of the normal range, bleeding and other related events will likely occur. On the other hand, if the PT INR values are found on the lower end of the spectrum, inappropriate blood clotting may occur.

When do PT INR values become abnormal?

There are several reasons why PT INR values become abnormal, and this could be due to:

  • Alcohol consumption
  • Wrong dosage of anticoagulants
  • Certain medications such as cold medicine, supplements, vitamins, oral contraceptives, antibiotics and hormone replacement therapy.
  • Disseminated intravascular coagulation
  • Obstruction of bile duct
  • Vitamin K deficiency
  • Malabsorption
  • Liver disease
  • Coagulation factor deficiency
  • Consuming foods that alter the effects of anticoagulant medications

The doctor may conduct further testing if the underlying cause of abnormal PT INR level is not established.

Is false reading of PT INR test result possible?

It is possible for false reading of the PT INR test result to occur, and this could be due to various factors such as:

  • Certain medications

Some medications can influence the effects of vitamin K and anticoagulants in a person’s body.  These include antibiotics, cimetidine, vitamin K supplements, aspirin, barbiturates, hormone replacement therapy and oral contraceptives. Herbal products can also make PT INR levels to become abnormal.

  • Dehydration

Dehydration, which can be due to vomiting and diarrhea, can also result to false reading of PT INR.

  • Eating foods rich in vitamin K

Consumption of foods high in vitamin K before the PT INR test will result in false-positive PT INR test result. Some of these foods are green tea, chickpeas, soybean products, turnip greens, broccoli, pork liver, beef liver and kale. Laxatives and alcoholic beverages can also result in abnormal PT INR levels.

PT INR normal values are very important in gauging the chances of stroke and bleeding. Patients need to talk with their doctors on how to keep the PT INR levels in check.

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Related posts:

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  2. Lipid profile normal values
  3. ESR – Normal Range, Low, High
  4. Normal Albumin Levels
  5. Hematocrit Levels-Normal, Low, High, Abnormal


  1. Linda D. says:

    I have a question. For 9 months, my PT INR count has been therapeutic, ie, 2.3 to 2.8. All of a sudden, this past month it plummeted to 1.7, which puts me at a dangerous risk for clotting. I had a bi-lateral pulmonary embolism about nine months ago and it is very important for me to maintain that level.

    One thing came to mind after I left the hematologist’s office. The “new” nurse had trouble getting the tube to fill, so in mid-stream of the blood passing into it, she yanked off that tube and put another one in its place. COULD this have cause a false reading, having the blood totally “stop” when it was draining; or even having air get to the blood when she changed the tubes. This resulted in an increased dosage from 10.0 to 12.5 mg. for a couple days to get me back “up there”. This past week, it was 3.0 so now I’m back on 10 mg. I’ll be on coumadin for life due to mutation of Factor V, protein deficiencies in C & S also, and more recently the pulmonary embolism.

    I would appreciate anyone shedding light on changing tubes and perhaps getting a false reading of the coumadin level. Thanks.



  2. Amanda says:

    Have you Changed your eating habits or diet 2month prior to taking test.

  3. Jerry Ingram says:

    I have a history of blood clots and have even had 2 PT’s in my right lung. I have my PTT/INR checked regularly. I am trying to get an injection in my left hip but the radiologist who does it wont because he says my blood is wrong. I have a INR of about 2.5. Another number he looks at 29.? but should be about 15.? My primary care doctor says he only looks at the 2.5 number. What is the 15.? number and how can I lower it from 29.? to the required 15.? that the radiologist requires before I can get the pain relief injection in my hip?


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