What the PT INR Test (Prothrombin Time) measures
The prothrombin time (PT) test measures how many seconds it takes for a sample of your blood plasma to form a clot in the laboratory. The result is also reported as the INR (international normalised ratio), which adjusts for differences between the chemicals used by different laboratories, so INR values can be compared from one test to the next and between laboratories. PT INR checks one part of the clotting system, which depends on several clotting proteins made by the liver, some of which need vitamin K. Its most common use is to monitor people taking warfarin or acenocoumarol, blood thinners that work by lowering these clotting proteins. Too low an INR means the medicine may not be protecting against clots; too high means a higher risk of bleeding, so the doctor adjusts the dose based on the result. PT INR is also checked before surgery or procedures, when there is unexplained bleeding or easy bruising, and in liver disease, where it helps show how well the liver is making clotting proteins. It does not test every part of clotting; the doctor may add other tests such as APTT or a platelet count. If you are on a blood thinner and have heavy bleeding, black stools, blood in urine or a severe headache, seek medical care urgently.
Price: the PT INR Test (Prothrombin Time) costs ₹264 at Pure Bliss (MRP ₹330), with the sample collected at our Action Area 2, New Town centre or at your home.
What the report includes
- Prothrombin time (seconds)
- Control time (seconds)
- INR (international normalised ratio)
Who this test is for
- People taking warfarin or acenocoumarol, for regular dose checks
- Before surgery or a planned procedure, as the doctor advises
- Unexplained bleeding, easy bruising or long bleeding after small cuts
- Liver disease, to see how well the liver makes clotting proteins
How to prepare, the sample, and when to expect the report
Preparation
No fasting is needed. If you take warfarin or acenocoumarol, keep taking it exactly as prescribed and do not change the dose before the test; tell us your current dose and when you last took it. Mention any other blood thinners, recent antibiotics or new supplements, as they can change the result.
Sample
Blood, from a vein in the arm (citrate tube for clotting tests).
Reporting time
Reported the same day if the sample is given before noon, else by the next day.
Reading the result
As commonly used guidance, the INR is around 1 in people who are not taking a blood thinner. For many people on warfarin the target INR is 2 to 3, though some conditions, such as certain mechanical heart valves, need a higher target set by the doctor. Your own report’s range and your doctor’s reading take priority over these general figures. Reference ranges differ between laboratories, so your report lists the laboratory’s own range beside each value. A result outside the range does not always mean illness; ask your doctor to explain it.
- Centre or home collection
- NABL-accredited Redcliffe Labs collection centre
- How collection works →
The PT INR Test (Prothrombin Time) can be booked at the clinic in Action Area 2 or with a home collection from 7:30 AM. Patients come to us from Action Area 1, Action Area 3, Rajarhat, Chinar Park, Salt Lake Sector V, Sukhobrishti and Eco Park.