Apollo Diagnostics | NABL-Certified Lab | No Fasting Required | Same-Day Digital Reports on WhatsApp
What is a PT / INR Test?
The Prothrombin Time (PT) test measures how long it takes for your blood to clot through the extrinsic coagulation pathway. The International Normalized Ratio (INR) is a standardised calculation derived from the PT result that accounts for differences in laboratory reagents and equipment — allowing consistent comparison of results across different laboratories worldwide. Together PT and INR are the primary tools for monitoring oral anticoagulant therapy (warfarin), diagnosing clotting disorders, assessing liver function and screening before surgical procedures.
⚠ Important for warfarin patients: If you are on warfarin, take your dose at the usual time after the blood collection — not before. Bring your warfarin dose card or anticoagulation clinic booklet to your appointment. Inform the phlebotomist of all medications you are taking as many drugs interact with warfarin and affect INR. No fasting is required.
Why is PT / INR Monitoring Vital?
PT/INR testing ensures your blood is in the therapeutic zone — not clotting too fast (risk of stroke or DVT) or too slow (risk of serious bleeding):
- Warfarin (Acitrom / Coumadin) Monitoring — the most common use; regular INR testing maintains warfarin dose in the therapeutic range (INR 2.0–3.0 for most indications)
- Pre-Surgical Screening — ensures safe clotting ability before surgery; INR above 1.5 is generally considered a risk for excessive surgical bleeding
- Liver Function Assessment — the liver produces clotting Factors II, V, VII, IX and X; abnormal PT/INR indicates impaired liver synthetic function in hepatitis, cirrhosis or liver failure
- Vitamin K Deficiency — Vitamin K is required to activate clotting factors II, VII, IX and X; deficiency causes elevated PT/INR
- Bleeding Disorder Investigation — diagnosing deficiencies of clotting factors in the extrinsic pathway (Factors I, II, V, VII, X)
- DIC (Disseminated Intravascular Coagulation) Monitoring — PT/INR is severely prolonged in DIC alongside elevated D-Dimer and low fibrinogen
Normal PT / INR Reference Ranges
| Category | PT (seconds) | INR |
|---|---|---|
| Normal (not on anticoagulants) | 11 – 13.5 seconds | 0.8 – 1.1 |
| Warfarin — Standard therapeutic range | Prolonged | 2.0 – 3.0 |
| Warfarin — Mechanical heart valve | Prolonged | 2.5 – 3.5 |
| Pre-surgical safe cut-off | Below 15 seconds | Below 1.5 |
| Mild prolongation | 15 – 20 seconds | 1.5 – 2.0 |
| Significant prolongation | Above 20 seconds | Above 2.0 (in non-anticoagulated patients) |
| Critically elevated (bleeding risk) | Above 35 seconds | Above 3.5 (even on warfarin) |
Understanding Therapeutic INR Targets for Different Conditions
Target INR ranges vary by clinical indication:
- Atrial Fibrillation (AF) stroke prevention — INR 2.0–3.0
- Deep Vein Thrombosis (DVT) treatment — INR 2.0–3.0
- Pulmonary Embolism (PE) treatment — INR 2.0–3.0
- Bioprosthetic (tissue) heart valve — INR 2.0–3.0 (usually only first 3 months)
- Mechanical mitral valve replacement — INR 2.5–3.5
- Mechanical aortic valve replacement — INR 2.0–3.0 or 2.5–3.5 depending on valve type
- Recurrent thromboembolism — INR 2.5–3.5
- Antiphospholipid Syndrome with arterial thrombosis — INR 3.0–4.0
PT vs APTT — Which Coagulation Test Do I Need?
| Test | Pathway Tested | Clotting Factors | Primary Use |
|---|---|---|---|
| PT / INR | Extrinsic pathway | Factors I, II, V, VII, X | Warfarin monitoring, liver function, pre-surgical screen |
| APTT (Activated Partial Thromboplastin Time) | Intrinsic pathway | Factors I, II, V, VIII, IX, X, XI, XII | Heparin monitoring, haemophilia screening, lupus anticoagulant |
| Both PT + APTT | Both pathways | All major factors | Comprehensive coagulation screen (DIC, bleeding disorder workup) |
When is a PT / INR Test Recommended?
Your doctor may recommend a PT/INR test if you:
- Are taking warfarin (Acitrom) and need routine INR monitoring (frequency depends on dose stability — typically weekly to monthly)
- Have had a recent warfarin dose change requiring re-check
- Are being screened before surgery, dental extraction or invasive procedure
- Have unexplained bruising, bleeding or prolonged bleeding from cuts
- Have liver disease (hepatitis, cirrhosis) requiring synthetic function assessment
- Are suspected of having a Vitamin K deficiency
- Have a family history of bleeding disorder (haemophilia, Factor VII deficiency)
- Are being investigated for DIC alongside elevated D-Dimer
- Need anticoagulation bridging during a medical procedure
What Affects INR in Warfarin Patients?
Many factors can raise or lower INR in patients on warfarin — making regular monitoring essential:
- Raise INR (increase bleeding risk) — antibiotics, antifungals, aspirin, NSAIDs, increased Vitamin K-rich food intake (spinach, kale, broccoli) suddenly decreased, alcohol, liver disease flares, fever
- Lower INR (decrease anticoagulation) — eating more Vitamin K-rich foods (green leafy vegetables), rifampicin (TB drug), some anticonvulsants, high-dose Vitamin C, reduced warfarin compliance, diarrhoea
- Key point — a consistent diet and medication routine helps keep INR stable. Sudden changes in diet or new medications require a re-check of INR within 5–7 days.
PT / INR Test Price in Kolkata
PT / INR Test Price: ₹460
No fasting required | Same-day results | Warfarin patients: take dose after collection | Free home collection above ₹2,000
No fasting required | Same-day results | Warfarin patients: take dose after collection | Free home collection above ₹2,000
Tests Commonly Ordered Alongside PT / INR
- APTT (Activated Partial Thromboplastin Time) — ordered alongside PT/INR for comprehensive coagulation screening and heparin monitoring
- Fibrinogen — low fibrinogen alongside prolonged PT/INR confirms DIC or severe liver failure
- D-Dimer — elevated in DIC alongside prolonged PT/INR and low fibrinogen
- Liver Function Test (LFT) — prolonged PT/INR from liver disease requires concurrent LFT assessment
- CBC (Complete Blood Count) — platelet count alongside PT/INR for complete haemostasis assessment
- Vitamin K levels — when Vitamin K deficiency is suspected as the cause of elevated INR
- Protein C & Protein S — natural anticoagulant proteins assessed alongside PT/INR in thrombophilia workup
Home Collection for PT / INR Test in Kolkata
Apollo Diagnostics provides home blood sample collection for PT/INR tests across Nagerbazar, Dum Dum, South Dum Dum and surrounding North and Central Kolkata areas. This is particularly convenient for warfarin patients who need regular monitoring and may have mobility limitations. Please inform the phlebotomist of your warfarin dose and the time of your last dose for accurate clinical correlation.
- Home collection available: 7:00 AM – 2:30 PM Daily
- No fasting required — book any time
- Warfarin patients: take your dose after collection, not before
- Same-day digital reports delivered to WhatsApp
- Free home collection on orders above ₹2,000
Quick Links
→ Apollo Diagnostics Nagerbazar → Blood Test near Arjunpur → Full List of Individual Tests → Book Home Collection → Full Body Checkup Packages
→ Apollo Diagnostics Nagerbazar → Blood Test near Arjunpur → Full List of Individual Tests → Book Home Collection → Full Body Checkup Packages
Frequently Asked Questions
Q1. What is the PT / INR test used for?
The PT/INR test measures blood clotting time through the extrinsic coagulation pathway. It is used to monitor warfarin (Acitrom) therapy, screen before surgery, assess liver synthetic function, detect Vitamin K deficiency and diagnose clotting factor deficiencies. The INR standardises the PT result across different laboratories for consistent warfarin monitoring.
Q2. What is the normal INR range?
Normal INR for people not on anticoagulants is 0.8–1.1. For patients on warfarin the standard therapeutic range is 2.0–3.0 for most conditions (AF, DVT, PE). Patients with mechanical heart valves typically target INR 2.5–3.5. INR above 3.5 on warfarin carries significant bleeding risk and requires urgent dose adjustment. Your cardiologist will specify your individual target range.
Q3. Does the PT / INR test require fasting?
No. The PT/INR test does not require fasting. Blood can be collected at any time. Warfarin patients should take their dose after blood collection — not before — for the most accurate result reflecting your steady-state INR. Inform your phlebotomist of your warfarin dose and timing.
Q4. What is the PT / INR test price at Apollo Diagnostics Kolkata?
The PT/INR test price at Apollo Diagnostics is ₹460. No fasting required. Same-day results via WhatsApp. Home collection is available free on orders above ₹2,000 — particularly convenient for warfarin patients needing regular monitoring.
Q5. How often should I get a PT / INR test if I am on warfarin?
When starting warfarin or after a dose change, INR should be checked every 3–5 days until stable. Once stable and within target range for 2–3 consecutive checks, the frequency is reduced to every 4–6 weeks. Stable long-term warfarin patients may be monitored every 6–8 weeks. Always re-check INR within 5–7 days after any new medication is started or stopped, after dietary changes or after illness — as these can significantly shift your INR.
Q6. What does a high INR mean for a warfarin patient?
A high INR (above the target range, e.g. above 3.0 for a patient targeting 2.0–3.0) means the blood is thinning more than desired, increasing the risk of serious bleeding. INR above 4.0 carries significant risk of spontaneous bleeding — in the brain, GI tract or other organs. Contact your cardiologist immediately for dose adjustment. INR above 5.0 with any signs of bleeding requires emergency evaluation.
Q7. Can diet affect INR?
Yes significantly. Vitamin K — found in green leafy vegetables like spinach, kale, broccoli and methi — directly antagonises warfarin and lowers INR. Sudden increases in Vitamin K intake (e.g. starting a salad diet) will lower your INR. Suddenly eating less of these foods will raise it. The key is consistency — keep your diet as stable as possible and always inform your doctor of major dietary changes so the warfarin dose can be adjusted accordingly.
Q8. Is home collection available for PT / INR test in Kolkata?
Yes. Apollo Diagnostics provides home blood sample collection for PT/INR tests across Nagerbazar, Dum Dum, South Dum Dum, Amarpalli, Motijheel, Arjunpur, Baguiati, Aswini Nagar, Satgachi, Lake Town, Bangur, Kaikhali, Sealdah, Entally, Phoolbagan, Tangra and surrounding areas. Particularly convenient for warfarin patients. Book by calling or WhatsApping +91 8660434628.
Q9. How long does it take to get PT / INR test results?
PT/INR test results are available the same day. Digital reports are delivered to your WhatsApp or email for immediate sharing with your cardiologist or treating physician.
Q10. Which centre processes my PT / INR sample in Kolkata?
All samples collected across North and Central Kolkata are processed at Apollo Diagnostics Nagerbazar — Nandarani Apartment, 8A Narasingha Avenue, Nagerbazar, Dum Dum, Kolkata 700074. Our lab is NABL-certified and ISO-certified using high-precision coagulation analyzers.
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