International Normalized Ratio (INR) |
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| It is important to have follow up blood tests as scheduled by your doctor and to know your Warfarin (Coumadin) dosage and INR. |
A laboratory test called an INR (International Normalized Ratio) measures the time it takes for blood to clot and compares it to an average. Monitoring the INR can be an important step in managing health.
To find the INR, a small sample of blood is taken from a fingertip or vein. The time it takes the blood to clot is measured. Then a ratio — an INR — is established.
The higher the INR, the longer it takes blood to clot. This can help prevent clots that may lead to strokes. But, if the INR is too high, there is a risk of uncontrolled bleeding. Report any unusual bleeding or bruising to your prescribing physician.
An INR is useful in monitoring the impact of anticoagulant (“blood thinning”) medicines, such as Warfarin (Coumadin). Patients with atrial fibrillation often take anticoagulant medications to protect against clots that can cause strokes. While taking Warfarin, patients have regular blood tests to monitor their INR. Just as patients know their blood pressure numbers, they also should know their Warfarin (Coumadin) dosage and their INR.
In healthy people, the INR is about 1.0. For patients on anticoagulants, the INR typically should be between 2.0 and 3.0 for patients with atrial fibrillation, or between 3.0 and 4.0 for patients with mechanical heart valves. However, the ideal INR must be individualized for each patient. An INR can be too high; a number greater than 4.0 may indicate that blood is clotting too slowly, creating a risk of uncontrolled bleeding. An INR less than 2.0 may not provide adequate protection from clotting.
GOOD TO KNOW: MEDICATIONS AND FOODS
Many drugs can change the INR such as: aspirin, ibuprofen, antibiotics, and birth control pills/progesterone-estrogen combination pills. Do not take any prescription or nonprescription medicines without first talking to the doctor who tracks your INR test results. Foods high in vitamin K, a natural blood-clotting factor, can alter an INR. Broccoli, lettuce, spinach and liver are all high in vitamin K. Doctors usually encourage patients to include these nutritious foods in a healthy diet. It is important, however, to consume a consistent amount of these foods and not drastically change eating habits. It is important to have follow up blood tests as scheduled by your doctor and to know your Warfarin (Coumadin) dosage and INR. Report any unusual bleeding or bruising to your prescribing physician.
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