There have not been enough studies don’t to indicate that cannabis can increase the chance of bleeding, but it is suggested that you take caution when combining cannabis and blood thinners or antiplatelet drugs, including warfarin (Coumadin), heparin, and clopidogrel (Plavix). Hemp could increase the anticoagulant effect of blood thinners by inhibiting its metabolism. It directly affects the anticoagulant properties of platelets in the blood. Therefore it naturally acts as a blood thinner and should rather be a replacement for blood thinning meds. More studies and understanding of Cannabis oil is needed. The lack of knowledge of how to use medical marijuana effectively leads to the advice of rather not using cannabis oils for patients using blood thinners for their clotting deficiency or other cardiac medical conditions. Please follow up with your primary care provider with this concern and seek his medical opinion.