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Private haematology · UK

Prothrombin Time - PT and INR, read properly.

A single venous sample, a UKAS-accredited haematology lab and a consultant haematologist reading anything that looks off.

See indicative pricing
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Indicative pricing

What private PT/INR testing costs in the UK.

Indicative ranges across our partner haematology labs.

In short

£35–£65, reported same day or next working day.

Test Indicative range
PT / INR (single test) £35–£65
Coagulation screen (PT, APTT, fibrinogen) £65–£110
Extended screen + D-dimer + thrombin time £130–£220
Factor assays (II, V, VII, IX, X) £180–£360
Mixing studies + inhibitor screen £220–£420
INR anticoagulant clinic (per visit) £75–£140
Haematology consultation only £220–£380

Prices vary by lab, by whether same-day reporting is needed and by whether factor assays or mixing studies are added.

The problem

A number without a reference range is not a result.

High-street PT/INR often comes back as a bare number, no ISI, no reagent, no companion tests - impossible to act on. We fix that.

  • The right panel, not just PT

    For anything other than warfarin monitoring, PT alone rarely answers the question. APTT, fibrinogen and platelets belong on the same request.

  • Reagent and ISI clearly stated

    Reference ranges change with reagent. Our reports print both, so any doctor - anywhere - can compare against their own lab.

  • A haematologist reads anything odd

    A raised PT in isolation, a mixing study that fails to correct, a sudden INR jump on stable warfarin - a consultant looks at it, not a template.

When it helps

When a PT/INR is the right test.

The situations we see most, plus the one red flag that means A&E rather than a routine appointment.

  • Warfarin monitoring

    Daily to monthly INR to keep you in target range (usually 2.0–3.0, or 2.5–3.5 for mechanical valves).

  • Pre-operative screen

    Before major surgery, dental extractions on anticoagulants, spinal or epidural blocks.

  • Unexplained bruising or bleeding

    Prolonged bleeding from cuts, heavy periods, easy bruising, nose bleeds - a starting point for a bleeding-disorder work-up.

  • Suspected liver disease

    The liver makes most clotting factors - a rising PT is one of the earliest signs of failing synthesis.

  • Vitamin K deficiency

    Malabsorption, prolonged antibiotics, poor diet, newborn haemorrhage risk.

  • DIC or sepsis work-up

    PT is part of the disseminated intravascular coagulation panel alongside APTT, fibrinogen and D-dimer.

  • Rare inherited factor deficiencies

    Factor II, V, VII, X deficiency - an isolated PT prolongation with a normal APTT.

  • Red flag: bleeding with INR over 8

    Any active bleeding on warfarin with an INR above 5, or any INR above 8 with or without bleeding, is an A&E problem - not a routine appointment.

Test options

PT is one number in a family of clotting tests.

What each test measures, and how they fit together to answer a specific clinical question.

  • Prothrombin time (PT)

    Seconds it takes plasma to clot after adding tissue factor. Measures the extrinsic and common pathways - factors II, V, VII, X and fibrinogen.

  • International Normalised Ratio (INR)

    PT expressed on a standard scale that accounts for reagent sensitivity (ISI). The universal number for warfarin dosing.

  • Activated partial thromboplastin time (APTT)

    The companion test for the intrinsic pathway. Prolonged in heparin therapy, haemophilia A/B, lupus anticoagulant.

  • Fibrinogen (Clauss)

    The final substrate for clot formation. Low in liver disease, DIC, dilutional coagulopathy; high in inflammation and pregnancy.

  • Mixing studies

    Patient plasma mixed 50:50 with normal plasma. Correction points to factor deficiency; failure to correct points to an inhibitor.

  • Individual factor assays

    Direct measurement of factor II, V, VII, IX, X activity for isolated PT or APTT prolongations.

  • Anti-Xa and DOAC levels

    Not measured by PT. If you are on apixaban, rivaroxaban, edoxaban or dabigatran, PT/INR is unreliable - an anti-Xa or DOAC-specific assay is used.

  • Point-of-care INR

    Fingerprick device (CoaguChek) for self-testing or clinic monitoring. Convenient but validated only for warfarin follow-up.

Safety and pitfalls

What to know before you read the number.

PT/INR is a safe venous test. The pitfalls are in preparation, interpretation and when the number needs urgent action.

  • A venepuncture, nothing more

    A single tube from a vein in the arm. Bruising is the commonest side effect - hold pressure for two minutes and it usually settles.

  • Sample handling matters

    Under-filled or delayed sodium citrate tubes give a falsely long PT. Our couriers deliver to the lab within four hours - not overnight.

  • Warfarin interactions are the everyday issue

    Antibiotics, amiodarone, statins, alcohol, cranberry juice, green leafy vegetables and St John’s wort all move the INR. Bring every tablet and supplement to the appointment.

  • PT is unreliable on DOACs

    Apixaban, rivaroxaban, edoxaban and dabigatran do not need INR monitoring. If a DOAC level is truly needed, we run an anti-Xa or dabigatran-specific assay instead.

  • Bleeding with a high INR is an A&E problem

    INR above 8, or any INR above 5 with active bleeding, needs vitamin K (oral or IV) and sometimes prothrombin complex concentrate - hospital, not a phone call.

  • A single abnormal PT is not a diagnosis

    A raised PT can come from lab error, sample dilution, medication or true coagulopathy. We repeat before we investigate, and investigate before we treat.

  • Pregnancy and the postpartum shift factors

    Fibrinogen and factors VII, VIII, X all rise in pregnancy. Reference ranges are different - obstetric haematology reads these differently.

  • Neonatal PT is a special case

    Newborns have physiologically prolonged PT from immature liver function and low vitamin K. Interpretation needs a paediatric-specific reference range.

  • Never stop warfarin on a lab result alone

    A raised INR on warfarin means dose review, not sudden stopping - stopping abruptly risks thrombosis. Always ring the anticoagulant clinic before changing.

Reading your report

Your PT/INR report in four parts. Read the last one first.

The bit that changes what you do is at the bottom - the impression. The rest is context.

A UK haematologist reviewing a coagulation report

A quiet reminder

A single number without its reference range and reagent is not a result - we always print both.

If you want us to talk you through the report and your warfarin dose, just ask.

  1. 01 Result

    PT seconds and INR

    The measured prothrombin time in seconds, and the derived INR. If you are on warfarin, only the INR matters clinically.

  2. 02 Reference

    Lab-specific reference range

    The normal PT range depends on the reagent used, so the number is always printed with the range - typically 10–14 seconds for PT and 0.8–1.2 for INR off warfarin.

  3. 03 Companion tests

    APTT, fibrinogen, platelets

    What the rest of the clotting screen shows - an isolated PT prolongation points to factor VII, a combined PT/APTT prolongation to liver disease or DIC.

  4. 04 Impression

    What it means and what to do next

    Read this first: whether the number is in range, whether your warfarin dose needs changing, whether a factor assay or specialist review is needed.

Recognised by major UK insurers

BupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealixBupaAXA HealthVitalityAvivaWPACignaHealix

PT/INR is usually covered when medically indicated. Routine anticoagulant monitoring is often outside insurance but affordably priced.

Frequently asked

Everything we get asked about PT and INR.

Quick answers on warfarin, DOACs, cost, turnaround and what a raised INR really means.

  • What is the difference between PT and INR?

    PT is the raw time in seconds it takes your plasma to clot after adding tissue factor. INR is that time normalised to a global standard using the reagent’s ISI value, so results are comparable between labs. Warfarin dosing uses INR, not PT.

  • Do I need to fast before a PT/INR test?

    No. PT/INR does not need fasting. Take your usual warfarin dose at the usual time, and bring a full list of every prescribed tablet, over-the-counter drug and supplement - many of them affect the result.

  • What is a normal INR?

    For a healthy adult not on anticoagulants, INR sits between 0.8 and 1.2. On warfarin the target depends on the reason: 2.0–3.0 for atrial fibrillation and most DVT/PE, 2.5–3.5 for mechanical mitral valves and recurrent thrombosis on treatment.

  • Does PT/INR work for people on apixaban or rivaroxaban?

    No. PT is unreliable on direct oral anticoagulants (DOACs). If a level is genuinely needed - before emergency surgery, in a bleed, or for reversal - we send an anti-Xa assay for apixaban/rivaroxaban/edoxaban, or a dilute thrombin time for dabigatran.

  • How quickly do I get the result?

    Same day for urgent cases, next working day for routine. The PDF report includes PT seconds, INR, reference range and - if abnormal - a consultant haematologist comment.

  • How much does a private PT/INR test cost in the UK?

    Roughly £35–£65 for a single PT/INR, £65–£110 for a full coagulation screen, and £180–£360 for factor assays.

  • My INR is 5 - should I worry?

    An INR above the target increases bleeding risk. If it is above 8, or between 5 and 8 with any bleeding, that is an A&E-level problem needing vitamin K and possibly prothrombin complex concentrate. If it is between the top of your target and 5 without bleeding, ring your anticoagulant clinic - do not stop warfarin on your own.

  • What causes a raised PT that is not from warfarin?

    The commonest reasons are liver disease, vitamin K deficiency, malabsorption, prolonged antibiotics, dilutional coagulopathy after transfusion, DIC and - rarely - inherited factor II, V, VII or X deficiency. A single raised result is repeated before it is investigated.

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