Prothrombin Time (PT) with International Normalized Ratio (INR) and Platelet Count
This test measures how long it takes for blood to clot (prothrombin time) and evaluates blood clotting factors relative to a standard, along with your platelet count.
["Helps assess bleeding risks and clotting disorders, often used to monitor medications like warfarin."]
Key facts at a glance
- LOINC
- 56471-6
- Short code
- DAT C3c-Sp Reag RBC Ql
- Synonyms
- DAT C3c-Sp Reag RBC Ql
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 4.2
- Ref high
- 5.9
- Critical range
- 2 N/A – 7 N/A
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 85041
- SNOMED
- 900000000000003001
- 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
Understanding Your Clotting Function
Prothrombin Time (PT) tests how long it takes for your blood to clot under controlled conditions. The INR compares your PT to a standard to identify clotting disorders or medication effects. This is often used to check for conditions like bleeding disorders or to monitor anticoagulant therapy.
Platelet Count Overview
Platelets are tiny blood cells that help prevent bleeding by forming clots. A lower than normal count may increase your risk of bleeding, while a higher count may raise concerns about clotting issues.
Why This Test Matters for Your Health
PT/INR and platelet counts are critical for diagnosing bleeding or clotting disorders, such as hemophilia or thrombocytopenia. They also help doctors adjust medications like warfarin to balance blood clotting safely.
Common Reasons for This Test
Your doctor may order this test if you have symptoms like excessive bleeding, unexplained bruising, or if you’re taking blood-thinning medications. It’s also used before surgeries or procedures to ensure safe clotting function.
Reference range
Adult males: 4.2-5.9; Females: 3.8-5.1 x 10^12/LN/A
No special preparation required. Stay well hydrated.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
◆Associated findings1
Short name
PT/INR + Platelet Count
Frequently asked questions
What does an abnormal result mean?
How often will I need this test?
Can I prepare for 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 17, 2026. · Read our editorial policy