Create Date: August 22, 2024
Last Modified Date: February 13, 2025
INR can be calculated with the following variables:
The result from this INR calculator will be a single number. This number is the measure of how quickly your blood can clot. Generally, a normal range for INR in a healthy individual would be between 0.8 and 1.1. In certain scenarios a number around 2.5 to 3.5 would be considered normal, it is all dependent on what your doctor believes to be the best value for your current health.
Calculating the INR of someone can be difficult. That is why we made this tool, to make it as simple and easy as possible to get that value. The steps include:
Let's say some students in medical school need to calculate the INR of each other during a class project. They can use this tool to help them with that. They measure their prothrombin time is 11 seconds and the control is 12. To use this tool we will enter 11 into the first field and then 12 into the second field. We will leave the international sensitivity index value as it is.
We can now hit calculate to get the INR value for the student. We find that the INR value is .893 which is falls into the range of generally normal for a healthy individual.
International normalized ratio, or INR, has its roots in the early 1900s when discovered prothrombin which was a major factor in blood coagulation.
In 1935, Armand Quick would develop the Prothrombin Time test which would measure how long it takes blood to clot after adding an enzyme called thromboplastin is introduced to it. Different sources of thromboplastin would begin to yield different results for different labs creating some inaccuracies.
Then in the 80s, the World Health Organization (WHO) would introduce the International Sensitivity Index (ISI) which would aim to reduce variations in results. ISI is assigned to each thromboplastin reagent based on its sensitivity to coagulant factors. This would directly lead to the creation of INR.
By the end of the 80s, the INR system would become widely adopted by laboratories all around the world. TO this day, INR is used in clinical settings for many reasons and has become more useful when applied certain ways with new technology.
According to Mayo Clinic, an INR of 1.1 or lower is normal for a healthy individual.
According to sources such as the NHS, if your INR is high, you should eat foods with vitamin K. This helps your body regulate INR levels more effectively.
Understanding INR can be difficult if some of the terms and keywords used are not ones you understand. Here we shed some more light on some of these terms.
| Term | Definition |
|---|---|
| Prothrombin | Prothrombin is a protein produced by the liver. It is one of many factors in the blood that help it to clot properly. |
| Thromboplastin | An enzyme secreted by injured cells, particularly platelets, that transforms prothrombin to thrombin during the first phases of blood clotting. |
| Prothrombin Time | A prothrombin time (PT) test measures how many seconds it takes for a clot to form in a blood sample. |
There are many interesting things that can be shared about international normalized ratio. Here are some of our favorites.
INR helped make a rat poison, Warfarin, a life-saving drug. INR would help ensure patients received the right about of this drug without causing excessive bleeding.
Foods rich in vitamin K, like spinach, kale, and broccoli, lower INR levels because vitamin K helps blood clot.
Many patients on long-term warfarin therapy can now check their INR at home using small finger-prick devices. This makes managing blood clot risk easier and more convenient without constant hospital visits.
