Blood Pressure: The Basics
This article covers what blood pressure is, how it is measured, and why it matters. It is general education only.
What is blood pressure?
Blood pressure is the force of blood pushing against the walls of your arteries. Arteries are the tubes that carry blood from the heart to the rest of the body. (Source: CDC)
It is measured in mm Hg. (Source: CDC)
What do the two numbers mean?
A blood pressure reading has two numbers. The first number is called systolic. The second number is called diastolic. (Source: CDC)
The systolic number is the pressure when the heart contracts (squeezes). The diastolic number is the pressure when the heart rests between beats. (Source: WHO)
The first number is higher than the second. (Source: NHS)
How is it measured?
A blood pressure test measures the pressure in your blood vessels. It uses a cuff that is inflated around the upper arm. (Source: NHS)
Automated home devices can be used, but evaluation by a health professional is still important for assessing risk. (Source: WHO)
Why it matters
High blood pressure usually has no symptoms. Getting it measured is the only way to find out if it is high. (Sources: NHS, WHO, CDC)
High blood pressure puts strain on the blood vessels, the heart, and organs such as the brain, kidneys, and eyes. (Source: NHS)
Higher blood pressure raises the risk of heart disease, heart attack, and stroke. It can damage the heart, brain, kidneys, and eyes. (Source: CDC)
High blood pressure that is not treated can lead to kidney disease, heart disease, and stroke. (Source: WHO)
Many people do not know they have it
The WHO estimates that about 600 million adults with hypertension (another name for high blood pressure) do not know they have it. That is 44% of adults with hypertension. These figures cover adults aged 30 to 79 around the world in 2024. (Source: WHO)
Where sources do not agree
Health organizations do not all use the same numbers to decide what counts as "high" blood pressure. The NHS also uses different numbers for checks in a clinic and checks at home. (Sources: CDC, WHO, NHS)
This article does not give any of those numbers. Please ask a health professional what they mean for you.
When to see a doctor
Most people with high blood pressure feel no symptoms. The sources say the only way to know is to get it measured. (Sources: NHS, WHO, CDC)
Very high blood pressure can sometimes cause symptoms. These include headaches, chest pain, dizziness, difficulty breathing, and blurred vision. The WHO says to seek care immediately if these symptoms happen together with high blood pressure. (Source: WHO)
If you feel unwell or have severe symptoms, such as chest pain or difficulty breathing, seek medical care.
About this article
This article was AI-assisted, reviewed by the author, and is not medical advice.