PT to INR Calculator
The PT to INR Calculator estimates your International Normalized Ratio (INR) based on your Prothrombin Time, Normal PT, and ISI value. This tool helps patients on blood thinners understand their clotting speed and verify treatment effectiveness. Use it to decode lab reports, check home monitor accuracy, or track daily health trends.
How International Normalized Ratio Is Calculated
The International Normalized Ratio (INR) measures how long it takes your blood to clot compared to a standard. It corrects for differences in lab equipment so your result is accurate no matter where you get tested.
INR = (Patient PT / Mean Normal PT)ISI
Where:
- Patient PT: Your blood clotting time in seconds.
- Mean Normal PT: The average clotting time for healthy people.
- ISI: The sensitivity of the chemicals used in the test.
First, we divide your PT time by the normal control time to find a ratio. Then, we raise that number to the power of the ISI. This step adjusts the math to match the specific chemicals used in your test. This method ensures your result is reliable and consistent with WHO guidelines.
By using these specific inputs, the calculator provides a standardized result that doctors trust for monitoring therapy.
What Your International Normalized Ratio Means
Your INR number tells you if your blood is clotting at a safe speed. A higher number means blood takes longer to clot, while a lower number means it clots faster. Understanding your specific range helps you manage your health safely.
Normal Healthy (1.0 – 1.4)
If you are not taking blood thinners, this is the standard target range. It indicates your clotting factors are working properly without any medication.
Therapeutic Range (2.0 – 3.0)
If you take Warfarin, this is usually your goal. This level prevents dangerous clots while keeping bleeding risk manageable. Maintain your current dose if you are in this range.
High Risk (Above 4.0)
This indicates your blood is too thin and you may bruise or bleed easily. Contact your doctor immediately, as they may need to adjust your dosage.
Important: Sudden changes in diet, like eating more Vitamin K found in leafy greens, can quickly lower your INR.
This calculator provides an estimate for informational purposes only and does not replace professional medical advice. Always consult your healthcare provider for diagnosis, dosage adjustments, and treatment.
Keep a log of your results to spot trends and discuss them during your next appointment.