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Carboxylated Vitamin K-Dependent Protein C (Protein C Activity)

Published: August 9, 2026Updated: August 16, 2026

This test measures the activity level of Protein C, a blood protein that helps prevent blood clots. It’s often checked in patients with blood disorders or those at risk of clotting issues.

Quick summary

["Protein C helps control blood clotting; low levels may increase clot risk."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
73930-0
Short code
RCS-4 5-carboxypentyl Bld Ql
Synonyms
RCS-4 5-carboxypentyl Bld Ql
Category
chemistry
Sample
whole-blood
Container
Lavender-top (EDTA)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
3 mL
Stability
Room temperature: 4h, Refrigerated: 24h
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why Is This Test Done?

Your doctor may order this test if you have symptoms of blood clots (like swelling, pain, or unexplained bruising), a history of clotting problems, or conditions like liver disease or antiphospholipid syndrome. It may also be part of routine monitoring for certain treatments.

What Does the Test Involve?

A blood sample is taken from a vein (usually in your arm). The sample is processed to measure Protein C activity. Results help assess your risk for clotting or bleeding disorders.

What Do Results Mean?

Results are compared to a standard range to determine if your Protein C activity is too high or too low. Very low levels may indicate a higher risk of clotting, while very high levels could suggest certain blood disorders or medications.

Common Conditions Affecting Results

Conditions like liver disease, severe infections, or certain medications (such as anticoagulants) can affect Protein C levels. Family history of clotting disorders may also play a role.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Protein C is a vitamin K-dependent protein that plays a key role in blood clotting regulation. Low levels can increase the risk of blood clots (thrombosis), while very high levels may rarely be associated with bleeding risks or other blood disorders. Regular monitoring may be needed if you have a history of clotting issues or take medications that affect clotting.

Short name

Protein C Activity (Carboxylated)

Frequently asked questions

What causes low Protein C levels?
Low Protein C levels can be caused by liver disease, vitamin K deficiency, certain medications (like anticoagulants), or inherited clotting disorders. Severe infections or pregnancy may also temporarily lower it.
What causes high Protein C levels?
High Protein C levels are less common but may occur with certain blood disorders, liver disease, or in response to medications. Rarely, it could be linked to inherited conditions or pregnancy-related changes.
How often should I get this test?
Your doctor will determine how often you need this test based on your medical history, symptoms, and treatment plan. Follow-up tests may be scheduled if you have ongoing clotting risks or conditions affecting Protein C levels.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy