A method of achieving safe and effective treatment or prevention of potentially harmful blood clots, or in inhibiting the coagulation of blood when so desired such as during a wide array of disease conditions including stroke, myocardial infarction, sickle-cell crisis and venous thrombosis, is provided by the administration of a fibrinogen-binding protein capable of binding at the N-terminal Bβ chain of fibrinogen, such as SdrG or Fbe, or their respective binding regions such as the A domain. In addition, compositions comprising effective amounts of the fibrinogen-binding proteins are also provided. The present anti-coagulation compositions have been shown to inhibit thrombin-induced fibrin clot formation by interfering with the release of fibrinopeptide B and the resulting anti-coagulation effects can be achieved without potential for causing or exacerbating unwanted side effects such as thrombocytopenia associated with prior art anticoagulants such as heparin.