Quick answer
The Prothrombin Time (PT/INR) Test costs ₹650 at Live Line Health Care. Times how quickly your blood clots and reports it as an INR. No fasting is needed. It uses a blood sample and the report is usually ready the same day. Book home sample collection or visit any of our 45 centres.
Also known as: Prothrombin Time, Prothrombin Time Test, PT INR, PT Test, INR Test, Prothrombin Time and INR, International Normalised Ratio, International Normalized Ratio
What is the PT/INR Test?
The Prothrombin Time (PT) test measures how many seconds your blood plasma takes to clot after the lab adds a reagent. Because reagents differ between labs, the result is also converted to the INR (International Normalised Ratio), a standard figure that can be compared from one lab to another. The test checks a group of clotting proteins, including factors II, V, VII and X and fibrinogen, most of which are made in the liver and several of which depend on vitamin K.
One of the main reasons for this test is monitoring blood thinners such as warfarin and acenocoumarol, given to people with mechanical heart valves, atrial fibrillation or clots in the legs or lungs. These medicines need a fine balance: too little leaves you open to clots, and too much can cause bleeding. Regular INR checks help your doctor adjust the dose. PT/INR is also used before surgery, for unexplained bleeding, and in liver disease, where it shows how well the liver is making proteins. The APTT checks a different arm of the clotting system and is the usual test for heparin, so the two are often ordered together.
What it measures: The time your plasma takes to clot through the extrinsic and common clotting pathways, in seconds, along with the standardised INR.
Parameters included (3)
- Prothrombin Time (PT)
- Control Time
- INR (International Normalised Ratio)
Why is this test done?
- Monitoring warfarin or acenocoumarol so that the dose can be adjusted
- Looking into easy bruising, nosebleeds or unexplained bleeding
- Assessing how well the liver is working in jaundice or long-term liver disease
- Checking clotting before surgery or an invasive procedure
- Detecting vitamin K deficiency, for example with poor absorption or long antibiotic courses
When should you get tested?
- You have started a blood thinner, or your dose has just been changed
- Bruises or bleeding gums while on a blood thinner
- A new antibiotic or other medicine added while on warfarin or acenocoumarol
- Yellow eyes, a swollen abdomen or other signs of liver disease
- A planned procedure where your doctor needs your clotting status
How to prepare for the PT/INR Test
- 1No fasting is needed. Keep to your regular diet, as sudden changes in green leafy vegetables can shift your INR.
- 2Take your blood thinner exactly as prescribed. Do not skip or delay a dose because of the test unless your doctor tells you to, and note the time of your last dose.
- 3Tell staff about new antibiotics, painkillers, or herbal and Ayurvedic products, which can change your INR.
- 4Carry your earlier INR values, so the new result can be compared with them.
- 5Press firmly on the puncture site for a few minutes afterwards, as it may bleed for longer when you are on a blood thinner.
PT/INR Test normal range
| Parameter | Typical reference range |
|---|---|
| Prothrombin time | 11–13.5 secondsdepends on the reagent; compare with the control on your report |
| INR, not on blood thinners | 0.8–1.1 |
| INR target on warfarin or acenocoumarol | Usually 2.0–3.0your doctor sets your own target |
| INR target with some mechanical heart valves | Usually 2.5–3.5your doctor sets your own target |
If you are on a blood thinner, the normal range printed on a report may not apply to you. The INR target given by your doctor is the number that matters. Ranges are typical adult values and vary between labs, age and sex. Always use the range printed on your report and discuss results with your doctor.
Understanding your results
- If you are not on a blood thinner, a high INR may point to liver disease, vitamin K deficiency, a clotting factor shortage or a serious condition called DIC. Your doctor will look for the cause.
- If you are on warfarin or acenocoumarol, an INR above your target means your blood is thinner than intended, which raises the risk of bleeding. Contact your doctor promptly and do not change the dose yourself.
- An INR below your target means less protection against clots, commonly because of missed doses, a change of diet or other medicines.
- A normal PT with a prolonged APTT points to a different part of the clotting pathway, and your doctor may consider causes such as haemophilia or heparin.
- Go to emergency care right away if you are on a blood thinner and have heavy bleeding, black stools, a severe headache or a head injury.
Health packages that include this test
The PT/INR Test is included in these full body checkups:
PT/INR Test – FAQs
What is the price of the PT/INR Test?
The Prothrombin Time (PT/INR) Test costs ₹650 at Live Line Health Care, at all 45 centres and for home sample collection.
What is the difference between PT/INR and APTT?
Both time how fast plasma clots, but they test different sets of clotting proteins. PT/INR is used for warfarin and acenocoumarol, and is sensitive to liver disease and low vitamin K. APTT is used for heparin and for bleeding conditions such as haemophilia. Doctors often order both.
What is a normal INR?
For a person not on a blood thinner, the INR is usually about 0.8 to 1.1. People on warfarin or acenocoumarol are kept higher on purpose, commonly between 2 and 3, and higher still for some heart valves. Your own target comes from your doctor, not from the printed range.
How often should INR be checked on a blood thinner?
Often at first, sometimes every few days until the dose settles. Once stable, many people test about every 4 weeks, although some can go longer. Test sooner if you start a new medicine, change your diet or fall ill. Your doctor will set the schedule that suits you.
Which foods affect INR?
Foods rich in vitamin K, such as spinach, amaranth, cabbage and other leafy greens, can lower the INR. You do not need to avoid them. What matters is eating a steady amount from week to week. Alcohol, some herbal products and new medicines can also change the result, so tell your doctor.
My INR is high. Should I stop my blood thinner?
Do not stop or skip doses on your own, as that can raise your risk of a clot or stroke. Contact the doctor who manages your blood thinner the same day and share your result. If you have bleeding, black stools or a severe headache, go to emergency care.
Why must the PT tube be filled to a certain level?
The tube holds a measured amount of a liquid that stops blood clotting until the test is run, and the balance between blood and liquid affects the result. If a tube is underfilled or the sample has clotted, the lab may ask for a fresh sample so that the reading is reliable.
Where can I get the PT/INR Test done?
At any of our 45 Live Line Health Care centres in 40 cities across Andhra Pradesh and Telangana, including Hyderabad, Visakhapatnam, Warangal, Kakinada and Nellore, or book home sample collection.
Medical disclaimer: This information is for general awareness only and is not a substitute for professional medical advice. Please consult a qualified doctor to interpret your results and before starting or changing any treatment.