Protein C is a natural blood protein that prevents excessive clotting.
Protein C is a natural protein in the blood that helps prevent excessive clotting. It is produced in the liver and becomes active when it interacts with another protein called thrombin. Once activated (Activated Protein C or APC), it works to slow down the clotting process by breaking down clotting factors (Factor Va and Factor VIIIa). This helps maintain a healthy balance so that blood clots form when needed (such as during injury) but do not grow too large or occur unnecessarily. A deficiency of Protein C can increase the risk of abnormal blood clots
Covid Safety
Assured
Free Report
Counselling
Recommended for You
How our test process works!
Overview
Protein C is a vitamin K–dependent protein produced by the liver.
It helps regulate blood clotting by inactivating Factor Va and Factor VIIIa, preventing excessive thrombosis.
Low Protein C levels increase the risk of abnormal clot formation (thrombophilia).
Risk Assessment
Protein C testing is typically done in people with:
High-Risk Situations
-
Unexplained or recurrent deep vein thrombosis (DVT)
-
Pulmonary embolism (PE) at a young age
-
Strong family history of clotting disorders
-
Warfarin-induced skin necrosis
-
Suspected inherited thrombophilia
-
Liver disease, severe infection, or DIC (disseminated intravascular coagulation)
-
Before prescribing certain medications that increase clot risk (e.g., estrogen therapy)
Normal Range (General Laboratory Reference)
Different labs may vary slightly. Typical reference ranges:
Protein C Activity Test
-
70–150% (functional activity)
Protein C Antigen Test
-
65–135% (protein quantity)
Note: Ranges depend on lab method, age, and health status; infants naturally have lower levels.
Interpretation
Low Protein C Levels May Indicate:
-
Inherited Protein C deficiency
-
Type I: low antigen + low activity
-
Type II: normal antigen + low activity
-
-
Liver disease (reduced production)
-
Vitamin K deficiency
-
Warfarin (Coumadin) therapy — lowers Protein C levels temporarily
-
DIC (disseminated intravascular coagulation)
-
Severe infection or sepsis
-
Kidney disease (protein loss)
High Protein C Levels
High levels usually have no clinical significance and are not associated with increased risk.
Sample Type
-
Blood sample (plasma)
-
Collected in a blue-top tube (sodium citrate anticoagulant)
-
Sample should be processed quickly to avoid false results
Frequently Asked Question
Protein C
Protein C is a natural blood protein that prevents excessive clotting.
Protein C is a natural protein in the blood that helps prevent excessive clotting. It is produced in the liver and becomes active when it interacts with another protein called thrombin. Once activated (Activated Protein C or APC), it works to slow down the clotting process by breaking down clotting factors (Factor Va and Factor VIIIa). This helps maintain a healthy balance so that blood clots form when needed (such as during injury) but do not grow too large or occur unnecessarily. A deficiency of Protein C can increase the risk of abnormal blood clots
Covid Safety
Assured
Free Report
Counselling