If you are taking warfarin to prevent clots your doctor will most likely choose to keep your INR between 2.0 and 3.0:
Depending on why you are taking the blood thinner, the desired level may be different.
Even when your INR stays between 2.0 and 3.0, you are more likely to have bleeding problems.
INR results higher than 3.0 may put you at even higher risk for bleeding.
INR results lower than 2.0 may put you at risk for developing a blood clot.
A PT result that is too high or too low in someone who is taking warfarin (Coumadin) may be due to:
The wrong dose of medicine
Taking certain over-the-counter (OTC) medicines, vitamins, supplements, cold medicines, antibiotics, or other medicines
Eating food that changes the way the blood-thinning medicine works in your body
Your provider will teach you about taking warfarin (Coumadin) the proper way.
This test is often done on people who may have bleeding problems. Their risk of bleeding is slightly higher than for people without bleeding problems.
Other slight risks can include:
Fainting or feeling lightheaded
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Multiple punctures to locate veins
Fink LM, Marlar RA, Miller JL. Antithrombotic therapy. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 42.
Schmaier AH, Miller JL. Coagulation and fibrinolysis. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 39.
Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.