Prothrombin Time (PT) with International Normalized Ratio (INR) and Reflex Testing for Coagulation Disorders
This test measures how long it takes for your blood to clot, helping assess liver function and blood clotting disorders. The INR provides a standardized comparison across labs.
["Evaluates blood clotting efficiency and liver health, critical for diagnosing bleeding risks or clotting issues."]
Key facts at a glance
- LOINC
- 75881-3
- Short code
- LA aPTT+dRVVT+PT W Reflex PPP
- Synonyms
- LA aPTT+dRVVT+PT W Reflex PPP
- Category
- chemistry
- 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
- Method
- coag
- 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 Matters for Your Health
Your liver produces proteins essential for blood clotting. If these proteins are missing or dysfunctional, bleeding or clotting problems may develop. This test checks your blood’s ability to clot and helps monitor conditions like liver disease or blood clotting disorders.
How the Test Works
Blood is drawn and mixed with a special solution. The time it takes for a clot to form is measured. The INR compares your result to a standard, ensuring consistent results across labs. Reflex testing may follow if initial results suggest a need for further evaluation.
Common Conditions Monitored
This test is often used to monitor patients with liver disease, blood clotting disorders (e.g., hemophilia), or those taking blood thinners like warfarin. It also helps screen for bleeding risks in people with certain genetic conditions or after surgeries.
What to Expect Before the Test
No special preparation is needed unless instructed by your healthcare provider. Wear comfortable clothing and arrive with your doctor’s orders if you’re on blood thinners. Avoid eating or drinking for 10 minutes before the draw if fasting is required (though not always applicable here).
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.
◆Associated findings1
Short name
PT/INR Profile
Frequently asked questions
Will I Need to Fast for This Test?
What Are Reflex Tests, and Do I Need to Worry?
Can I Take Blood Thinners 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