Prothrombin Complex Activity (Prothrombin Time) with INR Calculation, Serum/Plasma
This blood test measures how long it takes for your blood to clot and evaluates the function of certain blood proteins involved in clotting. It helps assess bleeding risks and identify issues with blood clotting pathways.
["Helps diagnose bleeding disorders, liver disease, or clotting problems by checking clot formation time and protein activity."]
Key facts at a glance
- LOINC
- 85359-8
- Short code
- PS-prothrom cmplx IgG SerPl IA-aCnc
- Synonyms
- PS-prothrom cmplx IgG SerPl IA-aCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- ia
- CPT
- 82784
- 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 Matters for Your Health
Your blood naturally clots to stop bleeding when a cut or injury occurs. This test checks how efficiently your blood clots by measuring the time it takes for a clot to form under controlled conditions. It also calculates the International Normalized Ratio (INR), a standardized way to compare results across labs.
What the Test Measures
The test evaluates the activity of several clotting factors (like prothrombin, factors VII, X, and protein C/S) in your blood. These factors work together to form a stable clot. The INR adjusts for differences in lab equipment and reagents, providing a consistent measure of clotting risk.
Common Conditions Monitored
This test is often used to monitor conditions like liver disease (where clotting factors may be produced poorly), blood clotting disorders (e.g., hemophilia), or patients on blood thinners (e.g., warfarin) to ensure safe dosing.
Preparation for the Test
No special preparation is needed, but you may be asked to fast for 12 hours before the test if your doctor specifies. Avoid aspirin or other blood-thinning medications unless cleared by your provider.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Elevated PT/INR may indicate liver disease, vitamin K deficiency, or medications that thin the blood. A prolonged test result suggests impaired clotting, while normal results confirm healthy clotting factor function. This test is critical for managing bleeding risks in high-risk patients.
Short name
Prothrombin Time (PT) with INR
Frequently asked questions
How long will I need to wait for results?
Can I eat or drink before this test?
Does this test require fasting?
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