Blood pressure is a measurement of the force against the walls of your arteries as your heart pumps blood through your body. Hypertension is another term used to describe high blood pressure.
Blood pressure readings are usually given as two numbers -- for example, 120 over 80 (written as 120/80 mmHg). One or both of these numbers can be too high.
The top number is called the systolic blood pressure. The bottom number is called the diastolic blood pressure.
Normal blood pressure is when your blood pressure is lower than 120/80 mmHg most of the time.
High blood pressure (hypertension) is when your blood pressure is 140/90 mmHg or above most of the time.
If your blood pressure numbers are 120/80 or higher, but below 140/90, it is called pre-hypertension.
If you have heart or kidney problems, or you had a stroke, your doctor may want your blood pressure to be even lower than that of people who do not have these conditions.
Causes, incidence, and risk factors
Many factors can affect blood pressure, including:
How much water and salt you have in your body
The condition of your kidneys, nervous system, or blood vessels
Your hormone levels
You are more likely to be told your blood pressure is too high as you get older. This is because your blood vessels become stiffer as you age. When that happens, your blood pressure goes up. High blood pressure increases your chance of having a stroke, heart attack, heart failure, kidney disease, or early death.
You have a higher risk of high blood pressure if:
You are African American
You are obese
You are often stressed or anxious
You drink too much alcohol (more than one drink per day for women and more than two drinks per day for men)
Most of the time, there are no symptoms. For most patients, high blood pressure is found when they visit their health care provider or have it checked elsewhere.
Because there are no symptoms, people can develop heart disease and kidney problems without knowing they have high blood pressure.
If you have a severe headache, nausea or vomiting, bad headache, confusion, changes in your vision, or nosebleeds you may have a severe and dangerous form of high blood pressure called malignant hypertension.
Signs and tests
Your health care provider will measure your blood pressure several times before diagnosing you with high blood pressure. It is normal for your blood pressure to be different based on the time of day.
All adults should have their blood pressure checked every 1 to 2 years if their blood pressure was less than 120/80 mmHg at their most recent reading.
If you have high blood pressure, diabetes, heart disease, kidney problems, or certain other conditions, have your blood pressure checked more often -- at least once every year.
Blood pressure readings taken at home may be a better measure of your current blood pressure than those taken at your doctor's office.
Make sure you get a good quality, well-fitting home blood pressure monitor. It should have the proper sized cuff and a digital readout.
Practice with your health care provider or nurse to make sure you are taking your blood pressure correctly.
Bring your home monitor to your appointments so your health care provider can make sure it is working correctly.
Your health care provider will do a physical exam to look for signs of heart disease, damage to the eyes, and other changes in your body.
If you have high blood pressure, you will have regular appointments with your doctor.
Even if you have not been diagnosed with high blood pressure, it is important to have your blood pressure checked during your yearly check-up, especially if someone in your family has or had high blood pressure.
Call your health care provider right away if home monitoring shows that your blood pressure is still high.
The same lifestyle changes you may follow to help control your blood pressure will also help prevent high blood pressure from occurring in most people.
Goldstein LB, Bushnell CD, Adams RJ, et al. Guidelines for the primary prevention of stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2011 Feb;42:517-84.
Victor, RG. Systemic hypertension: Mechanisms and diagnosis. In: Bonow RO, Mann DL, Zipes DP, Libby P, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 9th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 45.
Chobanian AV, et al. and the National High Blood Pressure Education Program Coordinating Committee. The seventh report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 report. JAMA. 2003;298:2560-2572.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Michael A. Chen, MD, PhD, Assistant Professor of Medicine, Division of Cardiology, Harborview Medical Center, University of Washington Medical School, Seattle, Washington. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.