Low INR Symptoms: What Does the International Normalized Ratio Test Result Mean?

People who are diagnosed with a blood clot or thrombosis may be prescribed by their healthcare provider with warfarin for treatment. Warfarin works by blocking the formation of substances in the blood that cause clotting.

Although warfarin can effectively prevent the formation of blood clots, it can also cause other serious health problems such as bleeding. To ensure the drug works effectively, patients taking warfarin may need routine blood tests to check the INR level.

What is INR?

INR stands for international normalized ratio, a standardized number that tells a person how long it takes for their blood to clot. It is measured with a blood test called prothrombin time (PT), which determines if the patient is receiving the correct dose of warfarin.

INR test is usually conducted in a laboratory or clinic, but it can also be done at home for some patients. For those who prefer home testing, they are required to use an in-home INR monitoring machine.

A patient's testing needs depend on how stable their INR is over time. According to the American Heart Association (AHA), patients should be tested at least once a month. There are cases where some patients will be required for tests as often as twice a week.

Prothrombin refers to a type of protein produced by the liver. It is one of the substances known for being a clotting factor. When a person gets a cut or other injuries that may cause bleeding, the clotting factors form a blood clot. How fast the blood clots depends on the amount of clotting factors in the blood and whether they work correctly.

If the blood clots too slowly, a person may bleed too much after an injury. If the blood clots too much, dangerous clots may form in the arteries or veins.

What are Low INR Symptoms?

A typical INR target ranges from 2 to 3, although it can vary from patient to patient.

INR levels that are too low indicate that a person is at risk for dangerous blood clots. Meanwhile, INR levels that are too high indicate that a person is at risk for dangerous bleeding.

If the INR of a person is below the target range, they are considered under-anticoagulated with an increased risk of blood clotting. In this case, a person may be deemed to have hypercoagulation.

Symptoms of increased blood clotting can differ depending on where the clot is. A blood clot in the abdomen causes abdominal pain, nausea, and vomiting. If the clot is in the arm or leg, a person may feel sudden or gradual pain, swelling, tenderness, and warmth of the limbs. The lungs can also be a target of blood clots, causing a person to experience shortness of breath and increased heart rate.

If the blood clot is present in the heart, a person may feel chest pain, sweating, and pain in the left arm. Meanwhile, symptoms of blood clots in the brain include trouble speaking, vision problems, seizures, and sudden severe headaches.