What is high blood pressure?

Blood pressure is a measure of how hard the blood pushes against the walls of your arteries as it moves through your body. It’s normal for blood pressure to go up and down throughout the day, but if it stays up, you have high blood pressure. Another name for high blood pressure is hypertension.

When blood pressure is high, it starts to damage the blood vessels, heart, and kidneys. This can lead to heart attack, stroke, and other problems. High blood pressure is called a "silent killer,'' because it doesn't usually cause symptoms while it is causing this damage.

Your blood pressure consists of two numbers: systolic and diastolic. Someone with a systolic pressure of 120 and a diastolic pressure of 80 has a blood pressure of 120/80, or "120 over 80."

• The systolic number shows how hard the blood pushes when the heart is pumping.
• The diastolic number shows how hard the blood pushes between heartbeats, when the heart is relaxed and filling with blood.

Adults should have a blood pressure of less than 120/80. High blood pressure is 140/90 or higher. Many people fall into the category in between, called prehypertension. People with prehypertension need to make lifestyle changes to bring the blood pressure down and help prevent or delay high blood pressure.

What causes high blood pressure?

In most cases, doctors can't point to the exact cause. But several things are known to raise blood pressure, including being very overweight, drinking too much alcohol, having a family history of high blood pressure, eating too much salt, and getting older.

Your blood pressure may also rise if you are not very active, you don't eat enough potassium and calcium, or you have a condition called insulin resistance.

What are the symptoms?

High blood pressure doesn't usually cause symptoms. Most people don't know they have it until they go to the doctor for some other reason.

Without treatment, high blood pressure can damage the heart, brain, kidneys, or eyes. This damage causes problems like coronary artery disease, stroke, and kidney failure.

Very high blood pressure can cause headaches, vision problems, nausea, and vomiting. Malignant high blood pressure (hypertensive crisis), which is blood pressure that rises very fast, can also cause these symptoms. Malignant high blood pressure is a medical emergency.

How is high blood pressure diagnosed?

Most people find out they have high blood pressure during a routine doctor visit. For your doctor to confirm that you have high blood pressure, your blood pressure must be at least 140/90 on three or more separate occasions. It is usually measured 1 to 2 weeks apart.

You may have to check your blood pressure at home if there is reason to think the readings in the doctor’s office aren't accurate. You may have what is called white-coat hypertension, which is blood pressure that goes up just because you're at the doctor’s office. Even routine activities, such as attending a meeting, can raise your blood pressure. So can commuting to work or smoking a cigarette.

How is it treated?