I've recently started taking warfarin because i have been diagnosed with a DVT. the odd thing is, whenever i go for my INR (bloodtest) It comes back saying ive taken nothing at all. I'm on a 10mg dose, i take it at the same time everyday with water.Yet when i see the doctor, she asks me questions like "are you sure you're taking warfarin? You know what warfarin looks like dont you?" It makes me feel very awkward.But i wouldnt lie about taking them..Why are my blood tests coming back negative?