Hemorrhage is the leading cause of preventable death after traumatic injury. Damage control resuscitation with a balanced ratio of blood products is key to avoiding the coagulopathy of trauma. Viscoelastic assays can help guide the transfusion of blood products after injury. Low-titer O whole blood (LTOWB) has experienced a resurgence in usage. Knowledge of individual blood components and indications for their use is essential for treating the hemorrhaging patient.