What Is Blood Pressure?
This information is for educational purposes only and should not replace medical advice. Always talk to your healthcare provider for medical decisions.
Most Important Things to Know:
Blood pressure is how hard your blood is pushing on your vessel walls.
Your blood pressure goes up and down during the day - this is usually normal!
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Your blood pressure is high or low depending on:
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How wide or narrow your arteries are ​
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How strongly your heart is pumping
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How much fluid you have in your body
What You'll Learn on This Page:
What Blood Pressure Is
Blood pressure is how hard your blood pushes on your blood vessel walls. It changes all the time to make sure every part of your body gets enough blood.
What Changes Your Blood Pressure
Your Blood Vessels
Your blood travels through tubes called blood vessels. The ones taking blood from your heart to your body are called arteries. The size of your arteries can change:
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They can get smaller to keep your blood pressure from going too low.
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They can get bigger to carry more blood.
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The arteries are the red lines. The blue lines are veins that carry blood to your heart.
Your Heart
Your heart is your body's pump. It moves blood around your body.
Your heart can:
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Pump more or less blood
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Push harder with each beat
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Beat faster or slower
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The more blood your heart pumps, the higher your blood pressure can be.​
The Amount of Fluid in Your Body
Your body can have too much or not enough fluid. This fluid is like water in your body. Don't worry—drinking water usually won't give you too much fluid. Your kidneys throw the extra water out. (But talk to your doctor about how much to drink if your heart or kidneys have problems.)​
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Too little fluid can lower blood pressure
This can happen if you:
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Lose a lot of blood
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Haven't been drinking enough water (called dehydration or being dehydrated)
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For example, being very sick, throwing up (vomiting), and can't drink much water
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Too much fluid can raise blood pressure
This can happen if you:
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Eat a lot of salt
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Have problems with your heart​​
A foot with swelling from too much fluid (called edema). The finger is pushing into the swelling. When it lets go, there will be an indent. That's because the fluid takes time to go back to where the finger was pushing.
Written by:
Last Updated: January 16, 2025
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Disclaimer: The information provided on this site is intended for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.