Blood pressure is often one of the first tests to be performed when visiting a doctor. This vital sign is a simple yet revealing measure of immediate health as well as an indicator of long-term health risks. A sudden drop in blood pressure can be a sign of serious dehydration, a severe infection or significant blood loss, while persistently high blood pressure, or hypertension, increases the risk of heart and blood vessel disease, stroke and kidney disease. Achieving normal blood pressure readings is a healthful goal, and while this doesn't rule out the possibility of disease, it's an important measure of good health.
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Blood Pressure Basics
Blood pressure is a measure of the force of blood pushing against the artery walls as the heart pumps blood throughout the body. Blood pressure is reported as a set of two numbers, expressed as mm Hg, or millimeters of mercury. When the blood pressure is stated as 110 over 70, or 110/70 mm Hg, the first number is the systolic pressure and the second is the diastolic. Systolic pressure reflects the force put on the arteries when the heart beats, and the diastolic number refers to the pressure in between heartbeats.
Normal Blood Pressure
The American Heart Association defines a normal blood pressure range for adults as systolic pressure below 120 and diastolic pressure below 80 -- or readings below 120/80 mm Hg. Blood pressure can get too low, typically a concern if readings are below 90/60 mm Hg or accompanied by symptoms such as dizziness, fainting, clammy skin, shallow breathing or fatigue.
Blood pressure readings can get too high, which is a risk for long-term health problems such as heart disease, kidney failure, erectile dysfunction and stroke. Prehypertension readings fall in the range of 120 to 130 over 80 to 89, and hypertension is considered readings above 140/90. Recommendations on when to treat hypertension with medications, and blood pressure targets when treated will be determined by your doctor. Treatment guidelines can vary by age, health condition and ethnic background, and are regularly updated by the Joint National Committee (JNC) on Prevention, Detection, Evaluation and Treatment of High Blood Pressure, with recent guidelines summarized in the February 2014 issue of "JAMA."
Factors That Influence Blood Pressure
Blood pressure readings can change for many reasons. Your readings can be influenced by factors such as age, ethnicity, gender, diet habits and physical fitness. Blood pressures are generally lower during sleep or at rest, and they increase with stress, anxiety or vigorous exercise. A single high blood pressure reading is generally of little concern, but consistently high readings require a medical evaluation.
If your blood pressure readings run too high or too low, you are at risk for both short-term and long-term health consequences. Have your readings checked on a regular basis, including home monitoring if recommended by your doctor. If your blood pressure readings are running outside of the normal range, be sure to follow your doctor's treatment recommendations for medications and lifestyle management, and call your doctor if your treatment plan does not get most of your readings within your target range. Also, seek immediate medical attention if your blood pressure readings are 180/110 or higher, or if you have high blood pressure along with blurry vision or a headache.
Reviewed by Kay Peck, MPH RD
- National Heart, Lung, and Blood Institute: Description of High Blood Pressure
- Neurology: Prehypertension and the Risk of Stroke -- A Meta-analysis
- Merck Manual: Overview of Hypertension
- JAMA: 2014 Evidence-Based Guideline for the Management of High Blood Pressure in Adults Report From the Panel Members Appointed to the Eighth Joint National Committee (JNC 8)