Prothrombin time (PT) is a blood test that measures how long it takes blood to clot. A prothrombin time test can be used to check for bleeding problems. PT is also used to check whether medicine to prevent blood clots is working. A PT test may also be called an INR test.

A PT/INR test helps find out if your blood is clotting normally. It also checks to see if a medicine that prevents blood clots is working the way it should.

Most of the time, results are given as what is called INR (international normalized ratio). If you are not taking blood thinning medicines, such as warfarin, the normal range for your PT results is: 11 to 13.5 seconds. INR of 0.8 to 1.1.

When the PT is high, it takes longer for the blood to clot (17 seconds, for example). This usually happens because the liver is not making the right amount of blood clotting proteins, so the clotting process takes longer. A high PT usually means that there is serious liver damage or cirrhosis.

Increased intake of supplements that contain vitamin K. High intake of vitamin K-rich foods. Fasting may reduce factors II, VII, and X, subsequently decreasing PT.

A prolonged PT means that the blood is taking too long to form a clot. This may be caused by conditions such as liver disease, vitamin K deficiency, or a coagulation factor deficiency (e.g., factor VII deficiency).

Some foods and other substances that may act as natural blood thinners and help reduce the risk of clots include the following list:

1. Turmeric. Share on Pinterest.
2. Ginger. Share on Pinterest.
3. Cayenne peppers. Share on Pinterest.
4. Vitamin E. Share on Pinterest.
5. Garlic.
6. Cassia cinnamon.
7. Ginkgo biloba.
8. Grape seed extract.

So, go bananas! But be sure to eat green bananas in normal portions and make sure you keep testing your regular blood test to make sure your INR doesn’t drop below your target range.

Two laboratory tests are used commonly to evaluate coagulation disorders: Prothrombin Time (PT) which measures the integrity of the extrinsic system as well as factors common to both systems and Partial Thromboplastin Time (PTT), which measures the integrity of the intrinsic system and the common components.

A result of 1.0, up to 1.5, is therefore normal. A low INR result means your blood is ‘not thin enough’ or coagulates too easily and puts you at risk of developing a blood clot. A high INR result means your blood coagulates too slowly and you risk bleeding.

Partial thromboplastin time (PTT) and activated partial thromboplastin time (aPTT) are used to test for the same functions; however, in aPTT, an activator is added that speeds up the clotting time and results in a narrower reference range.

Normal Values for Coagulation Tests

The average time it takes for blood to clot is 10 to 14 seconds.

A typical PT result is 10 to 14 seconds. Higher than that means your blood is taking longer than normal to clot and may be a sign of many conditions, including: Bleeding or clotting disorder. Lack of vitamin K. Lack of clotting factors.

The INR is derived from prothrombin time (PT) which is calculated as a ratio of the patient’s PT to a control PT standardized for the potency of the thromboplastin reagent developed by the World Health Organization (WHO) using the following formula: INR = Patient PT ÷ Control PT.

In healthy people an INR of 1.1 or below is considered normal. An INR range of 2.0 to 3.0 is generally an effective therapeutic range for people taking warfarin for disorders such as atrial fibrillation or a blood clot in the leg or lung.

PT/INR too high- If a PT/INR test result is too high, it means that the persons’ blood is clotting too slowly, and is at risk of bleeding; their dose of warfarin is too high. On the other hand, if the PT/INR test result is too low, their dose of warfarin may not be enough to protect the blood from clotting.

INR 4.5–10.0 Bleeding risk High.

The INR goal for people who take warfarin is usually from 2 to 3. A value higher than 3.5 increases the risk of bleeding problems.

People not taking warfarin have an INR of around 1 but patients with a mechanical heart valve should have an INR in the range of 2.5 to 3.5 to prevent their body creating a blood clot which could travel to the brain and cause a stroke.

PT results often are reported as an international normalized ratio (INR) that’s expressed as a number. A typical range for a person not taking blood thinner medication is 0.9 to about 1.1. For someone taking warfarin, the planned INR is usually between 2 and 3.5.

While the prothrombin time-international normalized ratio (PT-INR) range of 2.0 – 3.0 is recommended for Caucasians regardless of age and for non-elderly Japanese patients, the range of 1.6 – 2.6 has been recommended for elderly (age ≥ 70 years) Japanese patients [6–10].

An international normalized ratio (INR) higher than 9 is associated with a high risk of bleeding, yet most studies have focused on outpatients with lower INR.

A typical INR target ranges from 2-3 but can vary from patient to patient. Patients with a tendency towards clotting may have a range targeting 3-4, whereas patients with a higher bleeding risk may have a lower INR between 2-2.5.

A high INR was associated with an excess mortality: with an increase of 1 unit of INR above 2.5, the risks of death from cerebral bleeding (149 deaths) and from any cause were about doubled.

Stress may affect the length of time your medication stays in your system, potentially causing a spike in your INR levels. Science has shown that because of the effect stress can have on your body, vitamin K antagonists, such as warfarin, can stay in your system longer than normal causing a spike in INR levels.

Signs of bleeding or a high INR: Nosebleeds that do not stop. Gums bleed when you brush your teeth. Coughing up blood. Vomit (throw-up) that looks like coffee grounds.

It was concluded that caffeine has the capacity to inhibit the metabolism of warfarin and enhance its plasma concentration and hence anticoagulant effects. Thus, patients should be advised to limit the frequent use of caffeine-rich products i.e. tea and coffee during warfarin therapy.

They can make you feel green. Aside from bleeding-related issues, there are several side effects that have been linked to blood thinners, such as nausea and low counts of cells in your blood. Low blood cell count can cause fatigue, weakness, dizziness and shortness of breath.

Specifically, researchers found, patients on the clot-preventing drug warfarin showed a higher dementia risk if their blood levels of the medication were frequently too high or too low. And that was true not only for people with atrial fibrillation, but also for those using warfarin for other reasons.