Important complications of uncontrolled or poorly treated high blood pressure are due to chronic damage that occurs to different organs in the body and include heart attack, congestive heart failure, stroke, kidney failure, peripheral artery disease, and aneurysms (weakening of the walls of an artery, leading to a sac formation or ballooning of the artery wall). Aneurysms can be found in the brain, along the route of the aorta (the large artery that leaves the heart), and other arteries in the abdomen and extremities.

Many expert groups recommend a slightly higher target of 150/90 mmHg for those over somewhere between 60 and 80 years of age.[99][100][101][105] The JNC-8 and American College of Physicians recommend the target of 150/90 mmHg for those over 60 years of age,[13][106] but some experts within these groups disagree with this recommendation.[107] Some expert groups have also recommended slightly lower targets in those with diabetes[99] or chronic kidney disease with protein loss in the urine,[108] but others recommend the same target as for the general population.[13][103] The issue of what is the best target and whether targets should differ for high risk individuals is unresolved,[109] although some experts propose more intensive blood pressure lowering than advocated in some guidelines.[110]
Quitting smoking. Visit Smoking and Your Heart and the National Heart, Lung, and Blood Institute’s Your Guide to a Healthy Heart [PDF – 2MB]. Although these resources focus on heart health, they include basic information about how to quit smoking. For free help and support to quit smoking, you can call the National Cancer Institute’s Smoking Quitline at 1-877-44U-QUIT (1-877-448-7848).
In people aged 18 years or older hypertension is defined as either a systolic or a diastolic blood pressure measurement consistently higher than an accepted normal value (this is above 129 or 139 mmHg systolic, 89 mmHg diastolic depending on the guideline).[5][7] Other thresholds are used (135 mmHg systolic or 85 mmHg diastolic) if measurements are derived from 24-hour ambulatory or home monitoring.[79] Recent international hypertension guidelines have also created categories below the hypertensive range to indicate a continuum of risk with higher blood pressures in the normal range. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation and Treatment of High Blood Pressure (JNC7) published in 2003[27] uses the term prehypertension for blood pressure in the range 120–139 mmHg systolic or 80–89 mmHg diastolic, while European Society of Hypertension Guidelines (2007)[86] and British Hypertension Society (BHS) IV (2004)[87] use optimal, normal and high normal categories to subdivide pressures below 140 mmHg systolic and 90 mmHg diastolic. Hypertension is also sub-classified: JNC7 distinguishes hypertension stage I, hypertension stage II, and isolated systolic hypertension. Isolated systolic hypertension refers to elevated systolic pressure with normal diastolic pressure and is common in the elderly.[27] The ESH-ESC Guidelines (2007)[86] and BHS IV (2004)[87] additionally define a third stage (stage III hypertension) for people with systolic blood pressure exceeding 179 mmHg or a diastolic pressure over 109 mmHg. Hypertension is classified as "resistant" if medications do not reduce blood pressure to normal levels.[27] In November 2017, the American Heart Association and American College of Cardiology published a joint guideline which updates the recommendations of the JNC7 report.[88]
A blood pressure reading measures both the systolic and diastolic forces, with the systolic pressure listed first. The numbers show your pressure in units of millimeters of mercury (mm Hg)—how high the pressure inside your arteries would be able to raise a column of mercury. For example, a reading of 120/80 mm Hg means a systolic pressure of 120 mm Hg and diastolic pressure of 80 mm Hg.
An elevated blood pressure reading means that your blood pressure falls just above the normal level, corresponding to a systolic pressure between 120 and 129 or a diastolic pressure of 80 or less. The new guidelines eliminate the previous category of prehypertension. About one-fourth of Americans have elevated levels and they have two times the risk of heart disease compared with those who have lower blood pressures. Lifestyle changes can help many people with prehypertension lower their blood pressure.

Blood pressure often increases in stages. A person in her thirties may have mild to moderately elevated blood pressure readings. As she ages, blood pressure may continue to slowly rise. If someone develops high blood pressure before the age of 50, the risk of heart attack and stroke is greatly increased. If untreated, high blood pressure can reduce life expectancy by 10 or more years.
If these lifestyle changes don't lower your blood pressure to a safe level, your doctor will also prescribe medicine. You may try several kinds or combinations of medicines before finding a plan that works best for you. Medicine can control your blood pressure, but it can't cure it. You will likely need to take medicine for the rest of your life. Plan with your doctor how to manage your blood pressure.
The veins can expand and narrow. When veins expand, more blood can be stored in the veins and less blood returns to the heart for pumping into the arteries. As a result, the heart pumps less blood, and blood pressure is lower. On the other hand, when veins narrow, less blood is stored in the veins, more blood returns to the heart for pumping into the arteries, and blood pressure is higher.

If your blood pressure is always on the low side and you do not have any of the above symptoms, there is usually no cause for concern. Similarly, if you have a single at-home blood pressure reading that is abnormally low without any symptoms, you probably do not need to see your doctor. It is normal for your blood pressure to rise and fall over time, and your body is usually able to get your blood pressure back to normal.
The cuff is placed around the upper arm and inflated with an air pump to a pressure that blocks the flow of blood in the main artery that travels through the arm. The arm is held at the side of the body at the level of the heart, and the pressure of the cuff is gradually released. As the pressure decreases, a health practitioner listens with a stethoscope over the artery at the front of the elbow or an electronic machine senses the pulsation. The pressure at which the practitioner (or machine) first hears a pulsation from the artery is the systolic pressure (the top number). As the cuff pressure decreases further, the pressure at which the pulsation finally stops is the diastolic pressure (the bottom number). 

Effective lifestyle modification may lower blood pressure as much as an individual antihypertensive medication. Combinations of two or more lifestyle modifications can achieve even better results.[87] There is considerable evidence that reducing dietary salt intake lowers blood pressure, but whether this translates into a reduction in mortality and cardiovascular disease remains uncertain.[96] Estimated sodium intake ≥6g/day and <3g/day are both associated with high risk of death or major cardiovascular disease, but the association between high sodium intake and adverse outcomes is only observed in people with hypertension.[97] Consequently, in the absence of results from randomized controlled trials, the wisdom of reducing levels of dietary salt intake below 3g/day has been questioned.[96]

The NHLBI is part of the U.S. Department of Health and Human Services’ National Institutes of Health (NIH)—the Nation’s biomedical research agency that makes important scientific discovery to improve health and save lives. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders, including high blood pressure. Learn about the current and future NHLBI efforts to improve health through research and scientific discovery.
According to guidelines from the American Heart Association (AHA) and the American College of Cardiology (ACC), a reading below 120/80 mm Hg is classified as normal blood pressure. Those with a blood pressure reading anywhere from 120/80 up to 129/80 are classified within a category called elevated blood pressure. Hypertension is defined as a reading of 130/80 or higher.
Secondary hypertension results from an identifiable cause. Kidney disease is the most common secondary cause of hypertension.[23] Hypertension can also be caused by endocrine conditions, such as Cushing's syndrome, hyperthyroidism, hypothyroidism, acromegaly, Conn's syndrome or hyperaldosteronism, renal artery stenosis (from atherosclerosis or fibromuscular dysplasia), hyperparathyroidism, and pheochromocytoma.[23][47] Other causes of secondary hypertension include obesity, sleep apnea, pregnancy, coarctation of the aorta, excessive eating of liquorice, excessive drinking of alcohol, and certain prescription medicines, herbal remedies, and illegal drugs such as cocaine and methamphetamine.[23][48] Arsenic exposure through drinking water has been shown to correlate with elevated blood pressure.[49][50]
It has been shown that meditation and other relaxation techniques can help lower blood pressure. Yoga, tai chi, and breathing exercises can also help reduce blood pressure. It's best when these are combined with changes in diet and exercise. Tell your doctor if you are taking any herbal remedies, since some of these preparations can actually raise blood pressure or interact with your blood pressure medications. The following are supplements that may lower blood pressure:
Right after exercise is stopped, blood pressure decreases — often to levels a bit lower than normal resting blood pressure, and this effect can last for hours. Also, people who exercise regularly usually experience permanent improvements in resting blood pressure levels, as exercise strengthens the heart, helps with weight loss, improves circulation and lessens peripheral resistance — all factors that benefit blood pressure.
1. Concentrate on foods that lower blood pressure. Sugary, processed foods contain salt, sugar, damaged fats, and food sensitivities like gluten that contribute to or exacerbate high blood pressure. Shifting to a whole, unprocessed foods diet can dramatically impact your blood pressure. Many whole, unprocessed foods are rich in potassium, a mineral that supports healthy blood pressure. Some research shows that too much sodium and low amounts of potassium – can contribute to high blood pressure. Research shows people with high blood pressure can benefit from increased potassium in foods including avocado, spinach, wild-caught salmon, and sweet potatoes.
If elevated blood pressure levels are accompanied by diabetes, kidney disease, or cardiovascular disease, your doctor may suggest blood pressure medication as well lifestyle changes. If elevated levels are your only condition, lifestyle changes can help prevent blood pressure from rising. The following are lifestyle changes that may help lower blood pressure:

Low blood pressure due to nervous system damage (multiple system atrophy with orthostatic hypotension). Also called Shy-Drager syndrome, this rare disorder causes progressive damage to the autonomic nervous system, which controls involuntary functions such as blood pressure, heart rate, breathing and digestion. It's associated with having very high blood pressure while lying down.

Allergic reaction (anaphylaxis): Anaphylactic shock is a sometimes-fatal allergic reaction that can occur in people who are highly sensitive to drugs such as penicillin, to certain foods such as peanuts or to bee or wasp stings. This type of shock is characterized by breathing problems, hives, itching, a swollen throat and a sudden, dramatic fall in blood pressure.