Excessive blood loss in the short term is characterized by hypovolemic shock and is potentially fatal. According to the New York Times, hypovolemic shock can be caused by trauma, such as cuts and burns, in addition to diarrhea or profuse sweating.
Hypovolemic shock is caused by a drop in the overall volume of blood. This can be the result of an external or internal bleed, or it can be caused by a sudden loss of other body fluids such as sweat. In either case, the result is a net loss of blood that constitutes an acute medical emergency. According to the New York Times, symptoms of hypovolemic shock include cool, clammy skin, nausea, general weakness, rapid breathing, confusion, inability to urinate and syncope. Any of these symptoms merits a call for emergency medical evaluation.
Blood can also be lost gradually. Merck describes the symptoms of gradual blood loss as weakness, fatigue and pallor. Shortness of breath may also occur. Long-term hemorrhaging can lead to anemia. These symptoms can be caused by protracted losses of small amounts of blood. Blood lost in this way is referred to as occult blood, as it can be difficult to detect without a proper medical examination.