Classifying shock is useful in determining the patient’s hemodynamic response to injury or trauma. This will also help in estimating associated changes in the vital signs, mental, and kidney response. Class I shock is characterized by 750 mL or less blood loss with normal blood pressure. Class II shock is characterized by a blood loss of 750-1000 mL and slight hypotension. In class III, blood loss is 1,500-2000 mL, pulse rate is more than 120 bpm, respiratory rate is 30-40, and urinary output is 5-15ml/hour, with mild confusion. Class IV shock is characterized by a blood loss of more than 2000 mL, pulse rate is more than 140 bpm, respiratory rate is 35, urinary output is dismissible, with confusion and lethargy.