They must receive injections of platelets, which clot blood. Platelets interact with each other to seal wounds and prevent you from bleeding to death. Patients with more serious cases of hemophilia often get regular shots of the factor that they're missing — known as clotting factor replacement therapy — to prevent bleeding episodes. The clotting factors are transfused through an IV into a vein, and can be given in the hospital, at the doctor's office, or at home.