What Is High Blood Pressure?
What is high blood pressure and why is it dangerous? Get the answers to your blood pressure FAQs here.

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Picture of high blood pressure reading What Is High Blood Pressure?

At each doctor visit, one of the first things the nurse does is check your blood pressure. Why is this measurement so important? Here are the facts.

What is blood pressure?
Blood pressure measures the force of blood that travels through your arteries. If it's too high, it's a risk factor for heart disease, stroke and other complications. High blood pressure is often referred to as the "silent killer" because, most of the time, it has no symptoms.

Blood pressure is measured in millimeters of mercury (mm Hg). Readings are recorded as a fraction, with systolic pressure over diastolic pressure. For example: 120/80 mm Hg or "120 over 80."

  • Systolic pressure is the first or top number -- 120 in the example above. This is the pressure in your arteries when your heart beats.
  • Diastolic pressure is the bottom number -- 80 in the example. This is the pressure between heartbeats.

Blood pressure readings vary during the day, depending on your activity level. Blood pressure is often lower when you sleep and rises when you exercise.

What is "high?"
Hypertension (high blood pressure) has no symptoms, so your nurse or doctor will measure your blood pressure regularly during checkups. Your doctor will let you know how often you need it checked. High blood pressure is usually diagnosed after two or more high readings are recorded.

High blood pressure is classified as follows:

Category Systolic pressure (mm Hg)   Diastolic pressure (mm Hg)
Normal Less than 120 and Less than 80
Prehypertension 120-139 or 80-89
Hypertension
stage 1
140-159 or 90-99
Hypertension
stage 2
160 or higher or 100 or higher

Only one number -- systolic or diastolic -- has to be high to be diagnosed with high blood pressure.

The higher your blood pressure, the greater your chance for complications, such as heart attack, heart failure, stroke and kidney disease.

How is it treated?
High blood pressure is treated through lifestyle modifications and possibly medication.

Lifestyle changes include:

  • Reach or maintain a healthy weight. If you are overweight, lose weight. A weight loss of 10 pounds can often help lower blood pressure.
  • Follow the Dietary Approaches to Stop Hypertension (DASH) diet. Studies show that the DASH diet helps control high blood pressure. The diet is rich in vegetables, fruit and low-fat dairy. Foods high in saturated and total fat and cholesterol are limited. The DASH diet is also high in potassium. Adding more potassium-rich foods to your diet can help reduce blood pressure. Potassium can be found in many fruits and vegetables, beans/legumes, nuts and dairy products.
  • Limit sodium (salt) intake. Eating a diet high in sodium may raise your blood pressure and lead to heart disease and stroke. Experts now recommend limiting sodium intake to 1,500 mg (two thirds of a teaspoon) per day. 
  • Get active with your doctor's approval. Work up to 30 minutes of exercise most days of the week.
  • Limit alcohol. If you choose to drink, limit yourself to two drinks a day for a man or one drink a day for a woman.
  • Quit smoking. Smoking raises your risk for heart disease and other serious medical problems.

Changes to your lifestyle may not be enough to control your high blood pressure. Often, people need one medicine or more to control high blood pressure. Take your medication as your doctor prescribes.

What causes high blood pressure?
In 90 to 95 percent of the cases, the cause of high blood pressure is unknown. This type of high blood pressure is known as "essential hypertension."

Sometimes the cause of high blood pressure is known:

  • Secondary hypertension is high blood pressure that is caused by illness, such as kidney or adrenal gland problems.
  • Pregnancy-related hypertension is high blood pressure that develops during pregnancy.

How can I prevent it?
Follow these tips to help reduce your risk of high blood pressure:

  • Exercise regularly. Check with your doctor before you start an exercise program.
  • Lose weight if you are overweight.
  • Limit your salt intake. The recommendation for daily intake of sodium is less than 2,300 milligrams (mg). If you are over 50, African American or have high blood pressure, diabetes or chronic kidney disease, that number drops to 1,500 mg per day. Consuming less salt can help reduce blood pressure.
  • Limit alcohol.
  • Manage your stress. Stress can raise your blood pressure.
  • Don't smoke. If you do, quit.

Some risk factors for high blood pressure are out of your control, though:

  • Heredity. Like many diseases, high blood pressure tends to run in families.
  • Age. Your risk of developing high blood pressure increases as you age.
  • Race. African Americans get high blood pressure more often than Caucasians. High blood pressure usually starts at a younger age and it is often more severe.
By Jenilee Matz, MPH, Contributing Writer
Created on 06/24/1999
Updated on 11/28/2011
Sources:
  • National High Blood Pressure Education Program. The seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure.
  • Centers for Disease Control and Prevention. About high blood pressure.
  • U.S. Department of Agriculture. Dietary guidelines for Americans, 2010
Copyright © OptumHealth.
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