Prothrombin Time Test and INR (PT/INR)

Clinical Interpretation

If you were tested because you are taking warfarin or have certain health conditions, your results will probably be in the form of INR levels: INR levels that are too low may mean you are at risk for dangerous blood clots because your blood clots too easily. INR levels that are too high may mean you are at risk for dangerous bleeding because your blood is taking longer than normal to form a clot. If your INR is not normal, your provider will probably change your dose of warfarin. If you are not taking warfarin, your results may be in the form of a PT time, which is the number of seconds it takes for your blood sample to clot (prothrombin time). If you are not taking warfarin and your INR or prothrombin time results are not normal, it may be a sign of that your blood is not clotting normally. If your PT/INR levels are too low , your blood is clotting too quickly. This may be due to: A clotting disorder, a condition in which your body forms too many clots in arteries or veins. Clots can form when you don't have an injury, or they don't dissolve when they should. Supplements with vitamin K, or a diet high in vitamin K. Certain medicines. If your PT/INR levels are too high , your blood is clotting too slowly. This may be due to: A bleeding disorder, a condition in which your body can't clot blood well. When you have an injury or a procedure that may cause bleeding, it may cause too much bleeding. Liver disease. Vitamin K deficiency. Vitamin K plays an important role in blood clotting. Be sure to tell your provider if you are taking any medicines or supplements. Some may affect your results. Other things that may affect your PT/INR results include: Alcohol Foods high in vitamin K, such as green leafy vegetables Soybean and canola oils High-fat diets Ask your provider what you should avoid before your PT/INR test. To understand the results of a PT/INR test, your provider will consider your symptoms, medical history, and the results of other blood tests. Learn more about laboratory tests, reference ranges, and understanding results.

Medicare NCD code list — diagnoses CMS lists as supporting medical necessity

Showing 18 of 7,271 diagnoses CMS lists as covered for this test under NCD 190.17. The complete list is in CMS's Lab NCD code list; a listing is CMS's published code list, not a coverage determination for any claim.

Clinical Protocol & Patient Advice

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  If you are taking warfarin, you may need to delay your daily dose until after testing. Your provider will let you know if there are any other special instructions to follow.