High Blood Pressure

What Is High Blood Pressure?

Blood pressure is the force of blood pushing against the walls of the blood vessels as the heart pumps blood. If your blood pressure rises and stays high over time, it’s called high blood pressure. High blood pressure is dangerous because it makes the heart work too hard, and the high force of the blood flow can harm arteries and organs such as the heart, kidneys, brain, and eyes.

Systolic Pressure and Diastolic Pressure

The pressure of blood against the artery walls when your heart beats is called systolic pressure. The pressure between beats when your heart relaxes is called diastolic pressure.

Blood pressure is always given as two numbers, the systolic and diastolic pressures. Both are important. Usually they are written one above or before the other -- for example, 120/80 mmHg. The top, or first, number is the systolic and the bottom, or second number, is the diastolic. If your blood pressure is 120/80, you say that it is "120 over 80."

Your blood pressure changes throughout the day. It is usually lowest when you're asleep, and it rises when you awaken. It also can rise when you are excited, nervous, or active. So it varies throughout the day.

High Blood Pressure (Hypertension)

A systolic blood pressure of 140 mmHg or higher, or a diastolic blood pressure of 90 mmHg or higher, is considered high blood pressure, or hypertension. Hypertension is the medical term for high blood pressure.

If you have diabetes or chronic kidney disease, your recommended blood pressure levels are a systolic blood pressure of 130 mmHg or lower, and a diastolic blood pressure of 80 mmHg or lower.

High blood pressure currently affects nearly 1 in every 3 American adults.

Usually Has No Symptoms

High blood pressure is often called "the silent killer" because it usually has no symptoms. Occasionally, headaches may occur. Some people may not find out they have high blood pressure until they have trouble with their heart, kidneys, or eyes. When high blood pressure is not diagnosed and treated, it can lead to other life-threatening conditions, including heart attack, heart failure, stroke, and kidney failure. It can also lead to vision changes or blindness.

Possible Effects Over Time

Over time, high blood pressure can cause

Normal Blood Pressure Levels

A blood pressure reading of 120/80 mmHg or less is considered normal. Usually, the lower, the better, although very low blood pressure can sometimes be a cause for concern and should be checked out by your doctor.


If either your systolic or diastolic blood pressure is higher than normal (120/80) but not high enough to be considered high blood pressure (140/90), you have pre-hypertension. Pre-hypertension is a top number between 120 and 139 or a bottom number between 80 and 89 mmHg. For example, blood pressure readings of 138/82, 128/70, or 115/86 are all in the "pre-hypertension" range. (See the chart on the right for more information.)

If you have pre-hypertension, your chances of developing high blood pressure are greater than average unless you take action to prevent it. In fact, having pre-hypertension doubles a woman's chances of having heart disease or a stroke. That's a 100 percent increase. For men, the increase is 45 percent. Talk to your health care provider about lifestyle changes you can make to lower your blood pressure and prevent hypertension.

Isolated Systolic Hypertension

About two out of every three people over the age of 60 who have high blood pressure have isolated systolic hypertension. This means that only the top number, the systolic pressure, is high (140 mmHg or higher). Isolated systolic hypertension can be as harmful as when both numbers are high.

You may have isolated systolic hypertension and feel fine. As with other types of high blood pressure, it often causes no symptoms.

When your systolic and diastolic pressures fall into different categories, the more severe category is used to classify your blood pressure level. For example, 160/80 mmHg is considered stage 2 high blood pressure even though a diastolic pressure of 80 mmHg is in the pre-hypertension range.