I have been on warfarin since 2006. recently i've had inr results above 8.0 more than once. i've not changed my diet or dosage . i've always been therapeutic on current dosage until recently. what can the causes be for such elevated results ?

There are many factors that can affect the Warfarin level. It could be that your body is simply metabolizing the medicine differently and so your level went up. The dose will need to be adjusted once your INR is where it should be. Follow up with your doctor for instructions and for dose adjustment. Good luck to you!

An undiagnosed concomitant medical condition appears likely and aside from possible new drugs, supplements, recreational substances being among the most common culprits. Definitely worth a visit with your current prescriber and/or Coumadin clinic.