Shock is a life-threatening condition that occurs when the body is not getting enough blood flow. This can damage multiple organs. Shock requires immediate medical treatment and can get worse very rapidly.

Major classes of shock include:

• Cardiogenic shock (associated with heart problems)
• Hypovolemic shock (caused by inadequate blood volume)
• Anaphylactic shock (caused by allergic reaction)
• Septic shock (associated with infections)
• Neurogenic shock (caused by damage to the nervous system)

Shock can be caused by any condition that reduces blood flow, including:

• Heart problems (such as heart attack or heart failure)
• Low blood volume (as with heavy bleeding or dehydration)
• Changes in blood vessels (as with infection or severe allergic reactions)
• Certain medications that significantly reduce heart function or blood pressure

Shock is often associated with heavy external or internal bleeding from a serious injury. Spinal injuries can also cause shock.

Toxic shock syndrome is an example of a type of shock from an infection.