Prothrombin Time (PT) with International Normalized Ratio (INR) – Plasma
This test measures how long it takes for your blood to clot, helping assess liver function and blood clotting disorders.
["PT/INR checks blood clotting and liver health—critical for patients on blood thinners or with liver issues."]
Key facts at a glance
- LOINC
- 43575-0
- Short code
- C3PER
- Synonyms
- C3 Pcar-mCnc
- Category
- chemistry
- Sample
- serum
- Container
- Sterile, leak-proof container without preservatives; red-top or SST tube for serum component if paired testing is ordered
- Units
- N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- Method
- Immunonephelometry or Immunoturbidimetry
- CPT
- 86160
- SNOMED
- 38751000
- Specimen volume
- 1-2 mL of pericardial fluid minimum; 0.5 mL serum for paired testing
- Stability
- Pericardial fluid: Refrigerated (2-8°C) for up to 7 days; Frozen (-20°C or below) for up to 30 days. Avoid repeated freeze-thaw cycles.
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 24–72 hours
- Order
- routine
Why This Test Matters
Your PT/INR test evaluates the effectiveness of your blood clotting process. It does this by measuring the time it takes for a small cut or injury to form a clot. The INR standardizes this measurement across different labs, ensuring consistent results. This test is especially important if you have liver disease, take blood thinners (like warfarin), or have a bleeding or clotting disorder.
How the Test Works
Blood is drawn and mixed with a special chemical that triggers the clotting process. The time it takes for a clot to form is recorded. The INR compares your clotting time to a standard, helping doctors determine if your blood is clotting too quickly or too slowly.
What to Expect Before the Test
No special preparation is needed for this test. You may be asked to fast for 12 hours before blood is drawn, but this depends on your doctor’s instructions. Wear a comfortable shirt that allows easy access to your arm.
What to Expect During the Test
A healthcare professional will clean your arm with an antiseptic solution and insert a small needle to draw blood. You may feel a brief pinch or sting, but the procedure usually takes just a few minutes. The blood sample is then sent to a lab for testing.
Reference range
Reference ranges for complement C3 in pericardial fluid are not well-established; values should be interpreted in correlation with serum C3 levels and clinical context. Generally, complement levels in pericardial fluid may be lower than corresponding serum levels.N/A
No special patient preparation required for this test. However, pericardial fluid collection typically requires pericardiocentesis performed by a qualified physician under appropriate clinical conditions.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
Clinical Significance
Short name
PT/INR
Frequently asked questions
What does a high or low PT/INR result mean?
How often should I get this test?
Can lifestyle changes affect my PT/INR results?
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