Protein C (Blood)
Does this test have other names?
What is this test?
This test measures the level of protein C in your blood. Protein C helps your blood
If you have too little protein C (protein C deficiency), it means that your blood
may clot too much. Problems with blood clotting can be quite serious and possibly
fatal if a blood clot reaches the lungs (pulmonary embolism).
Having too much protein C doesn't often cause any health problems.
Protein C deficiency is an inherited condition. It can cause mild or severe symptoms,
depending on if you inherit one or two abnormal copies of the gene. About 1 in 500
people has a mild protein C deficiency, and about 1 in 4 million babies is born with
a severe protein C deficiency. Protein C deficiency may very rarely be acquired through
Even people with mild protein C deficiency are at risk for serious blood clots that
can be caused by:
Not moving around often
Why do I need this test?
You may need this test if you:
Had a blood clot in the past
Have a family member with a protein C deficiency
Have a family member with a blood clotting disorder
Have blood that does not clot normally
What other tests might I have along with this test?
Your healthcare provider may look for any other abnormalities in your blood that could
explain your blood clotting problems.
What do my test results mean?
Test results may vary depending on your age, gender, health history, the method used
for the test, and other things. Your test results may not mean you have a problem.
Ask your healthcare provider what your test results mean for you.
A normal level of protein C in the blood is between 70% and 150%. Lower-than-normal
readings may mean that you have a protein C deficiency.
A lower-than-normal level of protein C may be caused by:
Blood-thinning medicines, such as warfarin
Deficiency in vitamin K
Inherited protein C deficiency
Condition that causes the blood to clot too much (consumptive coagulopathy)
How is this test done?
The test is done with a blood sample. A needle is used to draw blood from a vein in
your arm or hand.
Does this test pose any risks?
Having a blood test with a needle carries some risks. These include bleeding, infection,
bruising, and feeling lightheaded. When the needle pricks your arm or hand, you may
feel a slight sting or pain. Afterward, the site may be sore.
What might affect my test results?
Taking certain medicines may affect your test results. If you take birth control pills,
you may have a lower-than-normal level of protein C in your blood.
How do I get ready for this test?
Your healthcare provider will tell you if you need to stop taking any of your usual
medicines before the test. Follow any directions you are given for not eating or drinking
before the test. Be sure your provider knows about all medicines, herbs, vitamins,
and supplements you are taking. This includes medicines that don't need a prescription
and any illegal drugs you may use.