Peptide C (Protein C Active) in Plasma
This test measures the active form of Protein C, a protein in your blood that helps prevent blood clots from forming too easily.
["Protein C helps regulate blood clotting and its levels can indicate risks for clotting disorders."]
Key facts at a glance
- LOINC
- 25570-3
- Short code
- C peptide sp12 p chal SerPl-sCnc
- Synonyms
- C peptide sp12 p chal SerPl-sCnc
- Category
- coagulation
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 0.8
- Ref high
- 1.2
- Critical range
- — – 5 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85610
- SNOMED
- 396252006
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
Why This Test Might Be Ordered
Your doctor may request this test if you have a history of blood clots, certain blood disorders, or if you’re taking medications that affect blood clotting. It may also be done before surgery or during pregnancy to assess your risk for clotting complications.
What to Expect Before the Test
No special preparation is needed, but you may need to fast for 8–12 hours before the test if it’s drawn from a vein. If drawn from a fingerstick, fasting isn’t required. Bring any medications or supplements you’re taking to your appointment.
What Happens During the Test
A healthcare provider will collect a blood sample from a vein in your arm. The blood will be processed to separate plasma, where the Protein C level is measured using a specialized lab technique.
What the Results Mean
Low levels of active Protein C may suggest an increased risk of blood clots, while very low levels could indicate a genetic or acquired disorder affecting clotting. High levels are less common but may be seen in certain conditions.
Reference range
INR: 0.8-1.2 (warfarin: 2.0-3.0)N/A
Inform your healthcare provider if you are taking blood thinners. No special preparation required.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Protein C plays a critical role in preventing excessive blood clotting. Abnormal levels can indicate conditions like thrombophilia (a tendency to form clots), liver disease, or certain medications (like anticoagulants) that alter clotting pathways. Monitoring Protein C helps guide treatment for clotting risks or bleeding disorders.
Short name
Active Protein C Level
Frequently asked questions
What causes Protein C levels to be low?
How is Protein C tested?
Can I eat or drink before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
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.
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