Massive gastrointestinal hemorrhage is a life-threatening condition that can result from numerous causes and requires skilled resuscitation to decrease patient morbidity and mortality. Successful resuscitation begins with placement of large-bore intravenous or intraosseous access; early blood product administration; and early consultation with a gastroenterologist, interventional radiologist, and/or surgeon. Activate a massive transfusion protocol when initial red blood cell transfusion does not restore effective perfusion or the patient's shock index is greater than 1.0. Promptly reverse coagulopathies secondary to oral anticoagulant or antiplatelet use. Use thromboelastography or rotational thromboelastometry to guide further transfusions. Secure a definitive airway and minimize aspiration.