Protein C test
Quick answer: A protein C test measures protein C, a natural substance in blood that helps stop clots from forming too easily. It is ordered after unexplained or repeated blood clots, or when there is a family history of protein C deficiency.
- SampleBlood
- TakesAbout 5 minutes
- Before the testYour doctor will choose the timing, as recent clots, pregnancy and blood thinners can affect results; do not stop any medicine on your own.
- In fertility careDoctors may check it before or during pregnancy if you or close family have had blood clots.
How the test is done
- 1Your doctor chooses a time away from a recent clot or blood thinner treatment if possible
- 2A vein is cleaned and blood is drawn into a blue-top tube
- 3The tube must be filled to the right level
- 4The sample is processed promptly in the lab
What your results can mean
Reading your report
Normal ranges differ between labs, so compare your result with the range printed on your report and discuss it with your doctor.
If the result is outside the usual range
A low protein C can be seen with an inherited deficiency, which raises the risk of clots, and also with liver disease, vitamin K deficiency, a recent clot or treatment with warfarin. High levels are not usually a concern.
Who usually has this test
People with unexplained or repeated blood clots, especially at a young age, and close relatives of people with protein C deficiency.
Risks and aftercare
Press firmly on the needle site, especially if you are on blood thinners.
Names and options
Also called: protein C activity, protein C deficiency test
Listed by the hospital as
- PROTEIN C, PLASMA
Questions about this test
Can warfarin affect a protein C test?
Yes. Warfarin lowers protein C, so the result may look low even without an inherited deficiency. Your doctor will plan the timing of the test, and you should not stop warfarin on your own.
Is protein C deficiency inherited?
It can be inherited from one or both parents, but low levels can also be caused by liver disease, vitamin K deficiency or a recent clot. Family testing may be suggested if an inherited cause is found.
Does protein C deficiency affect pregnancy?
It can raise the risk of blood clots in pregnancy and after birth. If you have it, your doctor may suggest preventive treatment during pregnancy.
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.
Get directions ↗IVF Pulse fertility care at Tamara Hospital →
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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.