1,25-dihydroxyvitamin D (calcitriol)
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INR/Prothrombin Time (Must reach the laboratory within 2 hours)
59.00
The INR / Prothrombin Time test measures how quickly your blood clots. It is essential for monitoring anticoagulant therapy and clotting disorders.
Turnaround time
Results available 5 days after arrival in lab. Doctor's report sent the day after results available (if required)
Biomarkers count
1
Same-Day Appointments
UKAS Accredited Labs
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Under 18? Patients under 18 can only be seen at GB Medlabs and Clinilabs, Monday to Friday only.
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Details about INR/Prothrombin Time (Must reach the laboratory within 2 hours)
What is the INR / Prothrombin Time test?
The Prothrombin Time (PT) test measures the time it takes for blood to clot via the extrinsic and common coagulation pathways. The INR (International Normalised Ratio) standardises PT results, allowing consistent comparison across laboratories.
This test evaluates the function of key clotting factors produced by the liver, including factors I, II, V, VII and X. It is particularly sensitive to deficiencies in vitamin K–dependent clotting factors.
INR/PT testing is a cornerstone of coagulation assessment, routinely used in clinical medicine to evaluate bleeding risk and monitor anticoagulant treatment.
Why do I need an INR / Prothrombin Time test?
Abnormal clotting can lead to dangerous bleeding or inappropriate clot formation. INR/PT testing helps ensure blood clotting is balanced and safe.
You may need an INR / PT test if you:
- Take warfarin or other vitamin K antagonists
- Require regular anticoagulation monitoring
- Have unexplained bruising or bleeding
- Have liver disease
- Are preparing for surgery or invasive procedures
- Have suspected clotting disorders
- Have vitamin K deficiency
Symptoms or conditions linked to abnormal INR/PT include:
- Easy bruising
- Nosebleeds or gum bleeding
- Prolonged bleeding from cuts
- Heavy menstrual bleeding
- Blood in urine or stool
- Liver-related conditions
Benefits of the INR / Prothrombin Time test
- Essential for warfarin monitoring
Ensures anticoagulation is within safe range. - Assesses bleeding risk
Identifies increased clotting time. - Evaluates liver clotting function
Reflects synthesis of clotting factors. - Standardised INR reporting
Allows consistent result interpretation. - Supports surgical safety
Confirms clotting status before procedures. - Detects vitamin K deficiency
Sensitive to vitamin K–dependent factors. - Clinically established test
Used routinely in NHS and private care. - Simple blood test
Requires only a single blood sample.
Step by step – how the test works
You can access INR / Prothrombin Time testing UK-wide through two options:
- Clinic appointment
Attend your nearest UK clinic, where a healthcare professional will take your blood sample. - At-home or hotel visit (£60 extra)
A qualified phlebotomist comes to your home or hotel, so you don’t need to travel.
Samples are processed promptly in an accredited UK laboratory to ensure accurate coagulation measurement.
Your results explained
Low INR / Short PT
Blood clots faster than normal, increasing clotting risk.
Typical UK interpretation:
- INR < 0.8
Normal INR / PT
Indicates normal clotting function in individuals not on anticoagulants.
Typical UK interpretation:
- INR 0.8–1.2
High INR / Prolonged PT
Blood takes longer to clot, increasing bleeding risk.
Typical UK interpretation:
- INR > 1.2
- Therapeutic warfarin range often 2.0–3.0 (condition-dependent)
Target INR ranges vary based on medical indication.
How It Works
Simple steps to get your results
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Book Online
Choose your test online and book in seconds. Select your preferred clinic location or home visit option.
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Visit or Test at Home
Attend one of our UK or London clinics, arrange a home nurse visit, or use a finger-prick kit where available.
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Get Your Results
Your sample is analysed by accredited UK laboratories, with secure results delivered directly to you.
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WhatsApp UsHow to Prepare for Your Test
Follow these guidelines for accurate results
Sample Timing
Where possible, attend your blood test between 7am and 12pm. Please wait until any short-term illness or infection has fully resolved before testing. Avoid intense exercise for 24–48 hours beforehand, as this can affect certain markers.
Fasting & Hydration
Fasting is not always required, but some tests may recommend it. If fasting is advised, avoid food for 8–12 hours before your appointment and drink water only. Stay well hydrated, as this helps with sample collection and accuracy.
Medications & Supplements
Continue prescribed medications unless advised otherwise by your clinician. Avoid vitamin, mineral, or biotin supplements for at least 24–48 hours before your test, as these can interfere with results. If you are unsure about any medication or supplement, please let us know before your appointment.
Hormones & Menstrual Cycle
For hormone-related tests, timing within your menstrual cycle may be important. If relevant, follow any specific guidance provided on your test page.
If you have any questions or special circumstances, our team is happy to advise before your appointment.
Frequently Asked Questions
To standardise clotting time and monitor anticoagulation.
INR is a calculated standardised form of PT.
No fasting is required.
As advised by your clinician, often every 1–4 weeks.
Yes. Vitamin K intake can influence results.
Yes. The liver produces clotting factors.
Yes. It is often required pre-procedure.
Yes. Many drugs interact with warfarin.
Yes. Home or hotel phlebotomy is available UK-wide for £60 extra.
Yes. Prompt medical review is important.
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