Pick your brains, please? I'm PV for at least 6 years; diagnosed after repeated DVTs while warfarinised. I take a daily dose of 9-10mg warfarin; INR target range 3-4. Now I'm to have a bone marrow biopsy to test for MF. So there is a a risk of bleeding, but I can't risk coming off anti-coagulants. Has anyone else gone through this procedure, and what steps did you take?