Onions (Allium Cepa and its close relatives, as opposed to Allium Sativum) contain potent coagulation modulators, as well as platelet inhibitors. Clinical, in vivo and in vitro testing confirms that the efficacy of commonly consumed quantities of onions in terms of the efficacy of its impact on coagulation and platelet function rivals and in many respects exceeds the potency of any other modalities available today. Additionally, onion compounds have unique effects as described later in this application. The use of onion extracts is thus proposed to prevent and treat acute and chronic cardiac and vascular complications and their sequelae, to prevent and treat thrombosis, to prevent and treat embolization in the setting of thrombosis, various arrhythmias and cardiac abnormalities, as well as to resolve hematomas