Merck Manual

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Quick Facts



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Last full review/revision Feb 2020| Content last modified Feb 2020
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What is shock?

Shock is a medical emergency caused by your organs not getting enough blood and oxygen. It has nothing to do with the "shock" we feel when something scares or upsets us. When your body can't get enough blood to your organs, those organs start shutting down. Your blood pressure is very low when you're in shock.

  • You can go into shock from losing too much blood, not having enough fluids in your body, or having heart problems, severe infections, or allergic reactions

  • Shock makes you feel weak, dizzy, and confused, and you may pass out

  • Doctors treat the cause of the shock and give you fluids, oxygen, and sometimes medicines to help raise your blood pressure

  • Without treatment, someone in shock will die

People in shock need emergency treatment. If you think someone is in shock:

  • Call 911 for an ambulance

  • Try to stop any major bleeding by putting pressure on the bleeding spot with a cloth

  • Lay the person down, covered for warmth with legs slightly raised

What causes shock?

Shock is caused by your organs (such as your brain, heart, and lungs) shutting down because they aren't getting enough blood. There are different types of shock depending on why your organs aren't getting enough blood:

  • Your body doesn't have enough blood or fluids, because you've bled a lot or are dehydrated

  • Your heart isn't pumping hard enough

  • Your blood vessels relax and get wider, which can happen if you have an allergic reaction, severe infection, poisoning, or damage to your nervous system

What are the symptoms of shock?

Symptoms of shock include:

  • Weakness, dizziness, and confusion

  • Cool, pale, sweaty skin

  • Fainting

  • Feeling sick to your stomach and vomiting

How can doctors tell if I am in shock?

Doctors know if you're in shock based on your symptoms and blood pressure. They'll do tests to figure out the cause if it isn't obvious based on your symptoms.

How do doctors treat shock?

Doctors will treat you in the hospital and give you:

  • Oxygen through a face mask or a breathing tube

  • IV fluids (fluids given into your vein through a thin plastic tube)

  • Blood transfusions if you lost a lot of blood

  • Sometimes, medicine to raise your blood pressure

Doctors also treat the cause of your shock, which may include giving other medicines or doing surgery.

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
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