Bio LabClotting tests (PT/PTT)
Reviewed by Dr. Sanaa Ghoneim, Medical laboratory specialist 21 October 2026
Home sample collection is available for this test
Ask about this test on WhatsAppWhat it measures
A clotting test measures how long your blood takes to clot. It includes two tests:
- PT (prothrombin time): reported together with the INR, a standard way of writing the result so it can be compared between laboratories.
- PTT (partial thromboplastin time): measures another part of the clotting process.
Both reflect clotting proteins, many of which are made by the liver.
Why a doctor may order it
- Following blood thinner treatment: PT/INR is used mainly with warfarin, and PTT may be used with heparin. Other blood thinners are usually followed differently, and your doctor decides which test you need.
- Before surgery or a procedure, to check clotting.
- Bleeding or bruising without a clear cause.
- A liver problem, since the liver makes the clotting proteins.
Preparation and fasting
A clotting test usually needs no fasting.
- If you take any blood thinner (such as warfarin or another anticoagulant), tell us its name and when you took your last dose.
- Do not stop your medicine or change the dose on your own. That is your doctor’s decision.
- Also tell us about any new medicines, supplements or herbal products, since some can affect clotting.
We confirm the preparation with you on WhatsApp before your appointment.
Sample type
A blood sample from a vein, usually in your arm, in a special tube for clotting tests. This tube must be filled to the right level and transported with care, and our technician takes care of this when drawing the sample at your home.
About your results
Your results reach you on WhatsApp. Discuss them with the doctor who ordered the test, who can explain them in light of your health, especially if you take a blood thinner.