Prothrombin Time (PT)/International Normalized Ratio (INR)
Prothrombin Time (PT)/International Normalized Ratio (INR) explained
PT/INR evaluates the extrinsic coagulation pathway and monitors warfarin therapy.
Varies by laboratory (LDT/CLIA; not FDA‑approved as a drug)Prothrombin Time (PT)/International Normalized Ratio (INR) helps treat
• Bleeding/clotting disorder evaluation
• Warfarin monitoring
• Pre‑procedure screening
additional medications
• Related clinical evaluation and history
• Repeat testing to confirm abnormal results
• Additional targeted labs as recommended
medication risks
• False positives/negatives leading to unnecessary anxiety or missed diagnoses
• Privacy and insurance implications depending on results
• Pre‑analytical variables (fasting, meds) can affect accuracy
side effects
• Bruising or soreness at draw site
• Lightheadedness or fainting (rare)
• Infection at puncture site (very rare)
FAQs
Q: Fasting?A: Not required.
Q: Diet interactions?
A: Vitamin K intake affects warfarin dosing.
Q: Medications?
A: Many drugs interact with warfarin—inform your clinician.
Q: Target INR?
A: Varies by indication—follow your prescriber.
Q: Same‑day results?
A: Common in clinics and labs.
