APTT (activated partial thromboplastin time)
Quick answer: The APTT test measures how long it takes your blood plasma to clot, checking one set of clotting factors. It is ordered for unexplained bleeding or clots, before surgery, to monitor heparin, and in the work-up for lupus anticoagulant.
- SampleBlood
- TakesAbout 5 minutes
- Before the testNo special preparation is usually needed; tell staff about any blood thinners you take.
- In fertility careA prolonged APTT can be a clue to lupus anticoagulant, part of antiphospholipid syndrome, which is checked after repeated miscarriages.
How the test is done
- 1Blood is drawn into a light-blue citrate tube
- 2The tube must be filled to the line for a valid result
- 3The lab adds reagents to your plasma
- 4The time taken to clot is measured in seconds
What your results can mean
Reading your report
Results are given in seconds and compared with a control; ranges differ between labs, so discuss them with your doctor.
If the result is outside the usual range
A long APTT can be seen with heparin treatment, haemophilia, von Willebrand disease, liver disease or lupus anticoagulant. A short APTT is usually not significant.
Who usually has this test
People with unusual bleeding or clotting, those on heparin, some people before surgery, and women with recurrent miscarriage.
Risks and aftercare
Bruising is possible; press for longer if you are on blood thinners.
Names and options
Also called: APTT, PTT, aPTT test
Listed by the hospital as
- APTT, PLASMA
Questions about this test
What is lupus anticoagulant?
It is an antibody that can make the APTT long in the lab but raises the risk of clots in the body. It is tested in women with recurrent miscarriage or past clots.
Why is APTT checked on heparin?
Heparin lengthens the APTT, so the test helps adjust the dose. Some hospitals use other tests instead.
How is APTT different from PT?
They check different sets of clotting factors. Using both helps narrow down the cause of a bleeding problem.
Related tests
Tamara Hospital & IVF Centre, Rajajinagar
34/3, 10th Cross Road, opp. Vardhaka Sardar Patel School, 1st N Block, 2nd Stage, Rajajinagar, Bengaluru 560010
The hospital is open 24 hours. Call before you come to check the timing for your scan or sample collection.
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This page explains each test in general terms so you know what to expect. It is not medical advice: your doctor decides which tests you need and what your results mean. Reference ranges differ between laboratories. Updated 4 November 2026.