Blood coagulation studies were conducted to determine the possible anti-/prothrombotic effect of an organic cannabis extract and the three major cannabinoids, THC, CBD and CBN. The in vitro effect of the cannabis extract on thrombin activity produced an IC50 value of 9.89 mg/ml, compared to THC at 1.79 mg/ml. It was also found that the extract, THC and CBN showed considerable inhibition of thrombin-induced clot formation in vitro with IC50 values of 600, 87 and 83 microg/ml for the extract, THC and CBN respectively. In an in vivo model used to determine clotting times of lean and obese rats treated with a cannabis extract, 50% clotting times were found to be 1.5 and 2 fold greater than their respective control groups, supporting the results obtained in the in vitro model. The study thus shows that Cannabis sativa and the cannabinoids, THC and CBN, display anticoagulant activity and may be useful in the treatment of diseases such as type 2 diabetes in which a hypercoagulable state exists.