INR Blood Test: Understanding Your International Normalized Ratio

An INR (international normalized ratio) blood test measures how long it takes for your blood to clot. This test is used to monitor the effects of blood thinners (anticoagulants), such as warfarin (Coumadin). INR blood tests are also used to monitor people with liver disease or other conditions that affect blood clotting.

The INR blood test measures the time it takes for the plasma in your blood to clot when chemicals are added to it. The results are reported as a ratio of the time it takes your plasma to clot compared with the time it takes normal plasma to clot.

A normal INR is between 2.0 and 3.0. However, the target INR for people taking warfarin may vary depending on their condition.

The INR blood test is a simple blood test that can be done in a doctor's office or a laboratory. The test results are usually available within a few days.

If you are taking warfarin, you may need to have INR blood tests regularly to make sure that the medication is working properly. The frequency of testing may vary depending on your condition and the stability of your INR.

Other medications that can affect INR levels include:

- Aspirin

- Clopidogrel (Plavix)

- Ibuprofen (Advil, Motrin)

- Naproxen (Aleve)

- Phenytoin (Dilantin)

- Rifampin (Rifadin)

Talk to your doctor or pharmacist if you are taking any medications that could affect your INR.