Protein C and Protein S Tests Test
Protein C and protein S tests measure the levels and function of two proteins that help prevent blood clots. Low levels or poor function mean a higher risk of abnormal clotting.
What this test measures
These tests measure how much protein C and protein S you have in your blood and how well they work. They help prevent blood from clotting too much.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
Higher than normal levels of protein C or S are not known to cause any health problems.
Lower-than-normal results
Lower than normal levels, or proteins that aren't working well, mean you have a higher risk of developing a blood clot. Your level of risk depends on how abnormal your test results are.
Frequently asked questions
What are protein C and protein S tests?
They are blood tests that measure how much protein C and protein S you have and how well they work. These proteins help prevent your blood from clotting too much.
Why might I need these tests?
Your provider may order them to find the cause of an unexplained blood clot, check your risk for future clots, or diagnose a protein C or S deficiency.
What does a low result mean?
A low level or poor function means you have a higher risk of developing a blood clot. The risk depends on how abnormal your results are.
Can a high result cause problems?
Higher than normal levels of protein C or S are not known to cause any health problems.
How can I lower my risk of blood clots if I have a deficiency?
Your provider may recommend blood thinners, treating the condition causing the deficiency, and avoiding things that increase clot risk like smoking and birth control pills.
Related lab tests
Sources
- MedlinePlus: Protein C and Protein S Tests — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.