Warfarin
Warfarin is an oral anticoagulant. It blocks vitamin K recycling in the liver, so the clotting factors that depend on vitamin K are made in an inactive form and blood clots more slowly. It is used to treat and prevent thrombosis and to reduce stroke risk in conditions that throw clots.
It is usually taken in the evening so a dose can be adjusted the same day the INR result arrives, and INR has to be checked regularly because the effect drifts. Vitamin K intake from greens should stay steady rather than be avoided, since it is the swings that move the INR; alcohol does the same and is not combined with it. Many common drugs shift the effect, including paracetamol, amoxicillin, azithromycin, fluconazole and omega-3 supplements, while acetylsalicylic acid, ibuprofen, diclofenac, naproxen, ketorolac and clopidogrel add bleeding risk on top and are avoided. Hemoglobin and platelets are followed alongside the INR.
Black or bloody stools, blood in urine or vomit, coughing blood, unexplained bruising, a nosebleed that will not stop, or any head injury are reasons to see a doctor at once.
Reference information, not medical advice. Discuss any change with your doctor.