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Quick Facts

Low Blood Pressure


The Manual's Editorial Staff

Last full review/revision Feb 2020| Content last modified Feb 2020
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What is low blood pressure?

Each heartbeat pushes blood through your arteries. Arteries are the blood vessels that carry blood from your heart to your body. Blood pressure is the pressure of blood in your arteries. Normal blood pressure keeps blood flowing through your body. High blood pressure strains your heart and can damage your arteries and other organs. Low blood pressure also can be dangerous.

  • Low blood pressure means your organs don't get enough blood

  • It can be caused by losing blood or being dehydrated

  • Low blood pressure makes you weak and dizzy and you might faint

  • Doctors will give you IV fluid and sometimes medicines to raise your blood pressure

  • If you've lost a lot of blood, you may need a blood transfusion

How is blood pressure measured?

Doctors use a blood pressure cuff to check your blood pressure. When blood pressure is checked, two numbers are recorded. For example, your blood pressure might be 120/80, called "120 over 80."

  • The higher number is the highest pressure in the arteries, which happens when your heart pushes the blood out

  • The lower number is the lowest pressure in the arteries, which happens when your heart is relaxed just before it begins to start to push blood out

What causes low blood pressure?

Low blood pressure can happen when:

  • You don't have enough fluid in your blood vessels

  • Your heart isn't pumping hard enough

  • Your blood vessels relax and get wider, which means there isn't enough fluid to keep them full

There are many problems that result in low blood pressure, including:

  • Loss of blood, such as from an injury or during surgery

  • Losing too much fluid (becoming dehydrated) from diarrhea, vomiting, or sweating a lot

  • Heart problems, such as a heart attack or an abnormal heart rhythm

  • Severe infections (sepsis)

  • Severe allergic reactions

  • Certain medicines

What are the symptoms of low blood pressure?

Symptoms may include:

  • Dizziness, particularly when you stand up

  • Weakness and confusion

  • Fainting

  • Cold, pale, sweaty skin

If your low blood pressure isn't treated, you may go into shock and even die.

How can doctors tell if I have low blood pressure?

Doctors measure your blood pressure with a blood pressure cuff. If you're very sick and in an intensive care unit (ICU), you may get a thin plastic tube in one of your arteries that's hooked up to a machine. The machine will constantly measure your blood pressure.

How do doctors treat low blood pressure?

Doctors need to treat the cause of low blood pressure. For example, if you're bleeding, they may do surgery to stop it. If you have an infection, they'll give you antibiotics. But whatever the cause, they need to raise your blood pressure.

The main treatment to raise your blood pressure is:

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

If you've lost a lot of blood, doctors may give you:

  • Blood transfusions

If your blood pressure is still low after you've had enough IV fluids and blood to fill up your blood vessels, doctors may give you medicines to raise your blood pressure. These medicines make your heart beat harder and make your blood vessels narrower. These medicines can be dangerous, so you'll be watched very closely while receiving them.

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