Overview

High blood pressure (hypertension) is a common condition in which the long-term force of the blood against your artery walls is high enough that it may eventually cause health problems, such as heart disease.

Blood pressure is determined both by the amount of blood your heart pumps and the amount of resistance to blood flow in your arteries. The more blood your heart pumps and the narrower your arteries, the higher your blood pressure. A blood pressure reading is given in millimeters of mercury (mm Hg). It has two numbers.

• Top number (systolic pressure). The first, or upper, number measures the pressure in your arteries when your heart beats.

• Bottom number (diastolic pressure). The second, or lower, number measures the pressure in your arteries between beats.

You can have high blood pressure for years without any symptoms. Uncontrolled high blood pressure increases your risk of serious health problems, including heart attack and stroke. Fortunately, high blood pressure can be easily detected. And once you know you have high blood pressure, you can work with your doctor to control it.

Symptoms

Most people with high blood pressure have no signs or symptoms, even if blood pressure readings reach dangerously high levels.

A few people with high blood pressure may have headaches, shortness of breath or nosebleeds, but these signs and symptoms aren't specific and usually don't occur until high blood pressure has reached a severe or life-threatening stage.

When to see a doctor

You'll likely have your blood pressure taken as part of a routine doctor's appointment.

Ask your doctor for a blood pressure reading at least every two years starting at age 18. If you're age 40 or older, or you're 18 to 39 with a high risk of high blood pressure, ask your doctor for a blood pressure reading every year.

Your doctor will likely recommend more-frequent readings if you've already been diagnosed with high blood pressure or have other risk factors for cardiovascular disease. Children age 3 and older will usually have blood pressure measured as a part of their yearly checkups.

Public blood pressure machines, such as those found in pharmacies, may provide helpful information about your blood pressure, but they may have some limitations. The accuracy of these machines depends on several factors, such as a correct cuff size and proper use of the machines. 

Causes

There are two types of high blood pressure.

Primary (essential) hypertension

For most adults, there's no identifiable cause of high blood pressure. This type of high blood pressure, called primary (essential) hypertension, tends to develop gradually over many years.

Secondary hypertension

Some people have high blood pressure caused by an underlying condition. This type of high blood pressure, called secondary hypertension, tends to appear suddenly and cause higher blood pressure than does primary hypertension. Various conditions and medications can lead to secondary hypertension, including:

• Obstructive sleep apnea

• Kidney disease

• Adrenal gland tumors

• Thyroid problems

• Certain defects you're born with (congenital) in blood vessels

• Certain medications, such as birth control pills, cold remedies, decongestants, over-the-counter pain relievers and some prescription drugs

• Illegal drugs, such as cocaine and amphetamines

Risk factors

High blood pressure has many risk factors, including:

• Age. The risk of high blood pressure increases as you age. Until about age 64, high blood pressure is more common in men. Women are more likely to develop high blood pressure after age 65.

• Race. High blood pressure is particularly common among people of African heritage, often developing at an earlier age than it does in whites. Serious complications, such as stroke, heart attack and kidney failure, also are more common in people of African heritage.

• Family history. High blood pressure tends to run in families.

• Being overweight or obese. The more you weigh, the more blood you need to supply oxygen and nutrients to your tissues. As the amount of blood flow through your blood vessels increases, so does the pressure on your artery walls.

• Not being physically active. People who are inactive tend to have higher heart rates. The higher your heart rate, the harder your heart must work with each contraction and the stronger the force on your arteries. Lack of physical activity also increases the risk of being overweight.

• Using tobacco. Not only does smoking or chewing tobacco immediately raise your blood pressure temporarily, but the chemicals in tobacco can damage the lining of your artery walls. This can cause your arteries to narrow and increase your risk of heart disease. Secondhand smoke also can increase your heart disease risk.

• Too much salt (sodium) in your diet. Too much sodium in your diet can cause your body to retain fluid, which increases blood pressure.

• Too little potassium in your diet. Potassium helps balance the amount of sodium in your cells. A proper balance of potassium is critical for good heart health. If you don't get enough potassium in your diet, or you lose too much potassium due to dehydration or other health conditions, sodium can build up in your blood.

• Drinking too much alcohol. Over time, heavy drinking can damage your heart. Having more than one drink a day for women and more than two drinks a day for men may affect your blood pressure.
  If you drink alcohol, do so in moderation. For healthy adults, that means up to one drink a day for women and two drinks a day for men. One drink equals 12 ounces of beer, 5 ounces of wine or 1.5 ounces of 80-proof liquor.

• Stress. High levels of stress can lead to a temporary increase in blood pressure. Stress-related habits such as eating more, using tobacco or drinking alcohol can lead to further increases in blood pressure.

• Certain chronic conditions. Certain chronic conditions also may increase your risk of high blood pressure, including kidney disease, diabetes and sleep apnea.

Sometimes pregnancy contributes to high blood pressure as well.

Although high blood pressure is most common in adults, children may be at risk, too. For some children, high blood pressure is caused by problems with the kidneys or heart. But for a growing number of kids, poor lifestyle habits — such as an unhealthy diet and lack of exercise — contribute to high blood pressure.

Complications

The excessive pressure on your artery walls caused by high blood pressure can damage your blood vessels as well as your organs. The higher your blood pressure and the longer it goes uncontrolled, the greater the damage.

Uncontrolled high blood pressure can lead to complications including:

• Heart attack or stroke. High blood pressure can cause hardening and thickening of the arteries (atherosclerosis), which can lead to a heart attack, stroke or other complications.

• Aneurysm. Increased blood pressure can cause your blood vessels to weaken and bulge, forming an aneurysm. If an aneurysm ruptures, it can be life-threatening.

• Heart failure. To pump blood against the higher pressure in your vessels, the heart has to work harder. This causes the walls of the heart's pumping chamber to thicken (left ventricular hypertrophy). Eventually, the thickened muscle may have a hard time pumping enough blood to meet your body's needs, which can lead to heart failure.

• Weakened and narrowed blood vessels in your kidneys. This can prevent these organs from functioning normally.

• Thickened, narrowed or torn blood vessels in the eyes. This can result in vision loss.

• Metabolic syndrome. This syndrome is a group of disorders of your body's metabolism, including increased waist size, high triglycerides, decreased high-density lipoprotein (HDL) cholesterol (the "good" cholesterol), high blood pressure and high insulin levels. These conditions make you more likely to develop diabetes, heart disease and stroke.

• Trouble with memory or understanding. Uncontrolled high blood pressure may also affect your ability to think, remember and learn. Trouble with memory or understanding concepts is more common in people with high blood pressure.

• Dementia. Narrowed or blocked arteries can limit blood flow to the brain, leading to a certain type of dementia (vascular dementia). A stroke that interrupts blood flow to the brain also can cause vascular dementia.

Diagnosis

Blood pressure measurement

Your doctor will ask questions about your medical history and do a physical examination. The doctor, nurse or other medical assistant will place an inflatable arm cuff around your arm and measure your blood pressure using a pressure-measuring gauge.

Blood pressure measurements fall into several categories:

• Normal blood pressure. Your blood pressure is normal if it's below 120/80 mm Hg.

• Elevated blood pressure. Elevated blood pressure is a systolic pressure ranging from 120 to 129 mm Hg and a diastolic pressure below (not above) 80 mm Hg. Elevated blood pressure tends to get worse over time unless steps are taken to control blood pressure. Elevated blood pressure may also be called prehypertension.

• Stage 1 hypertension. Stage 1 hypertension is a systolic pressure ranging from 130 to 139 mm Hg or a diastolic pressure ranging from 80 to 89 mm Hg.

• Stage 2 hypertension. More-severe hypertension, stage 2 hypertension is a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher.

• Hypertensive crisis. A blood pressure measurement higher than 180/120 mm Hg is an emergency situation that requires urgent medical care. If you get this result when you take your blood pressure at home, wait five minutes and retest. If your blood pressure is still this high, contact your doctor immediately. If you also have chest pain, vision problems, numbness or weakness, breathing difficulty, or any other signs and symptoms of a stroke or heart attack, call local emergency medical number.

Both numbers in a blood pressure reading are important. But after age 50, the systolic reading is even more important. Isolated systolic hypertension is a condition in which the diastolic pressure is normal (less than 80 mm Hg) but systolic pressure is high (greater than or equal to 130 mm Hg). This is a common type of high blood pressure among people older than 65.

Because blood pressure normally varies during the day and may increase during a doctor visit (white coat hypertension), your doctor will likely take several blood pressure readings at three or more separate appointments before diagnosing you with high blood pressure.

Taking your blood pressure at home

Your doctor may ask you to record your blood pressure at home to provide additional information and confirm if you have high blood pressure.

Home monitoring is an important way to confirm if you have high blood pressure, to check if your blood pressure treatment is working or to diagnose worsening high blood pressure.

Home blood pressure monitors are widely available and inexpensive, and you don't need a prescription to buy one. Home blood pressure monitoring isn't a substitute for visits to your doctor, and home blood pressure monitors may have some limitations.

Make sure to use a validated device, and check that the cuff fits. Bring the monitor with you to your doctor's office to check its accuracy once a year. Talk to your doctor about how to start checking your blood pressure at home.

Devices that measure your blood pressure at your wrist or finger aren't recommended by the American Heart Association because they can provide less reliable results.

Tests

If you have high blood pressure, your doctor may recommend tests to confirm the diagnosis and check for underlying conditions that can cause hypertension.

• Ambulatory monitoring. This 24-hour blood pressure monitoring test is used to confirm if you have high blood pressure. The device used for this test measures your blood pressure at regular intervals over a 24-hour period and provides a more accurate picture of blood pressure changes over an average day and night. However, these devices aren't available in all medical centers, and they may not be reimbursed.

• Lab tests. Your doctor may recommend a urine test (urinalysis) and blood tests, including a cholesterol test.

• Electrocardiogram (ECG or EKG). This quick and painless test measures your heart's electrical activity.

• Echocardiogram or  2D echo : Depending on your signs and symptoms and test results, your doctor may order an echocardiogram to check for more signs of heart disease. An echocardiogram uses sound waves to produce images of the heart.

Overview

Low blood pressure might seem desirable, and for some people, it causes no problems. However, for many people, abnormally low blood pressure (hypotension) can cause dizziness and fainting. In severe cases, low blood pressure can be life-threatening.

A blood pressure reading lower than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic) is generally considered low blood pressure.

The causes of low blood pressure can range from dehydration to serious medical disorders. It's important to find out what's causing your low blood pressure so that it can be treated.

Symptoms

For some people, low blood pressure signals an underlying problem, especially when it drops suddenly or is accompanied by signs and symptoms such as:

• Dizziness or lightheadedness

• Fainting

• Blurred or fading vision

• Nausea

• Fatigue

• Lack of concentration

Shock

Extreme hypotension can result in this life-threatening condition. Signs and symptoms include:

• Confusion, especially in older people

• Cold, clammy, pale skin

• Rapid, shallow breathing

• Weak and rapid pulse

When to see a doctor

If you have signs or symptoms of shock, seek emergency medical help.

If you have consistently low blood pressure readings but feel fine, your doctor will likely just monitor you during routine exams.

Even occasional dizziness or lightheadedness may be a relatively minor problem — the result of mild dehydration from too much time in the sun or a hot tub, for example. Still, it's important to see your doctor if you have signs or symptoms of low blood pressure because they can point to more-serious problems. It can be helpful to keep a record of your symptoms, when they occur and what you're doing at the time.

Causes

Blood pressure is a measurement of the pressure in your arteries during the active and resting phases of each heartbeat.

• Systolic pressure. The top number in a blood pressure reading is the amount of pressure your heart produces when pumping blood through your arteries to the rest of your body.

• Diastolic pressure. The bottom number in a blood pressure reading refers to the amount of pressure in your arteries when your heart is at rest between beats.

Current guidelines identify normal blood pressure as lower than 120/80 mm Hg.

Blood pressure varies throughout the day, depending on:

• Body position

• Breathing rhythm

• Stress level

• Physical condition

• Medications you take

• What you eat and drink

• Time of day

Blood pressure is usually lowest at night and rises sharply on waking.

Blood pressure: How low can you go?

What's considered low blood pressure for you may be normal for someone else. Most doctors consider blood pressure too low only if it causes symptoms.

Some experts define low blood pressure as readings lower than 90 mm Hg systolic or 60 mm Hg diastolic. If either number is below that, your pressure is lower than normal.

A sudden fall in blood pressure can be dangerous. A change of just 20 mm Hg — a drop from 110 systolic to 90 mm Hg systolic, for example — can cause dizziness and fainting when the brain fails to receive enough blood. And big drops, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening.

Conditions that can cause low blood pressure

Medical conditions that can cause low blood pressure include:

• Pregnancy. Because the circulatory system expands rapidly during pregnancy, blood pressure is likely to drop. This is normal, and blood pressure usually returns to your pre-pregnancy level after you've given birth.

• Heart problems. Some heart conditions that can lead to low blood pressure include extremely low heart rate (bradycardia), heart valve problems, heart attack and heart failure.

• Endocrine problems. Parathyroid disease, adrenal insufficiency (Addison's disease), low blood sugar (hypoglycemia) and, in some cases, diabetes can trigger low blood pressure.

• Dehydration. When your body loses more water than it takes in, it can cause weakness, dizziness and fatigue. Fever, vomiting, severe diarrhoea, overuse of diuretics and strenuous exercise can lead to dehydration.

• Blood loss. Losing a lot of blood, such as from a major injury or internal bleeding, reduces the amount of blood in your body, leading to a severe drop in blood pressure.

• Severe infection (septicemia). When an infection in the body enters the bloodstream, it can lead to a life-threatening drop in blood pressure called septic shock.

• Severe allergic reaction (anaphylaxis). Common triggers of this severe and potentially life-threatening reaction include foods, certain medications, insect venoms and latex. Anaphylaxis can cause breathing problems, hives, itching, a swollen throat and a dangerous drop in blood pressure.

• Lack of nutrients in your diet. A lack of the vitamin B-12, folate and iron can keep your body from producing enough red blood cells (anemia), causing low blood pressure.

Medications that can cause low blood pressure

Some medications can cause low blood pressure, including:

• Water pills (diuretics), such as furosemide (Lasix) and hydrochlorothiazide (Microzide, others)

• Alpha blockers, such as prazosin (Minipress)

• Beta blockers, such as atenolol (Tenormin) and propranolol (Inderal, Innopran XL, others)

• Drugs for Parkinson's disease, such as pramipexole (Mirapex) or those containing levodopa

• Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor) and imipramine (Tofranil)

• Drugs for erectile dysfunction, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Alyq, Cialis), particularly when taken with the heart medication nitroglycerin (Nitrostat, others)

Types of low blood pressure

Doctors often break down low blood pressure (hypotension) into categories, depending on the causes and other factors. Some types of low blood pressure include:

• Low blood pressure on standing up (orthostatic or postural) hypotension). This is a sudden drop in blood pressure when you stand up from a sitting position or after lying down.
  Gravity causes blood to pool in your legs when you stand. Ordinarily, your body compensates by increasing your heart rate and constricting blood vessels, thereby ensuring that enough blood returns to your brain.
  But in people with orthostatic hypotension, this compensating mechanism fails and blood pressure falls, leading to dizziness, lightheadedness, blurred vision and even fainting.
  Orthostatic hypotension can occur for various reasons, including dehydration, prolonged bed rest, pregnancy, diabetes, heart problems, burns, excessive heat, large varicose veins and certain neurological disorders.
  A number of medications also can cause orthostatic hypotension, particularly drugs used to treat high blood pressure — diuretics, beta blockers, calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors — as well as antidepressants and drugs used to treat Parkinson's disease and erectile dysfunction.
  Orthostatic hypotension is especially common in older adults, but it also affects young, otherwise healthy people who stand up suddenly after sitting with their legs crossed for long periods or after squatting for a time.

• Low blood pressure after eating (postprandial hypotension). This drop in blood pressure occurs one to two hours after eating and affects mostly older adults.
  Blood flows to your digestive tract after you eat. Ordinarily, your body increases your heart rate and constricts certain blood vessels to help maintain normal blood pressure. But in some people these mechanisms fail, leading to dizziness, faintness and falls.
  Postprandial hypotension is more likely to affect people with high blood pressure or autonomic nervous system disorders such as Parkinson's disease.
  Eating small, low-carbohydrate meals; drinking more water; and avoiding alcohol might help reduce symptoms.

• Low blood pressure from faulty brain signals (neurally mediated hypotension). This disorder, which causes a blood pressure drop after standing for long periods, mostly affects young adults and children. It seems to occur because of a miscommunication between the heart and the brain.

• Low blood pressure due to nervous system damage (multiple system atrophy with orthostatic hypotension). Also called Shy-Drager syndrome, this rare disorder has many Parkinson disease-like symptoms. It 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.

Risk factors

Low blood pressure (hypotension) can occur in anyone, though certain types of low blood pressure are more common depending on your age or other factors:

• Age. Drops in blood pressure on standing or after eating occur primarily in adults older than 65. Neurally mediated hypotension primarily affects children and younger adults.

• Medications. People who take certain medications, for example, high blood pressure medications such as alpha blockers, have a greater risk of low blood pressure.

• Certain diseases. Parkinson's disease, diabetes and some heart conditions put you at a greater risk of developing low blood pressure.

Complications

Even moderate forms of low blood pressure can cause dizziness, weakness, fainting and a risk of injury from falls.

And severely low blood pressure can deprive your body of enough oxygen to carry out its functions, leading to damage to your heart and brain.

Diagnosis

The goal in testing for low blood pressure is to find the cause. Besides taking your medical history, doing a physical exam and measuring your blood pressure, your doctor might recommend the following:

• Blood tests. These can provide information about your overall health as well as whether you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia or diabetes) or a low red blood cell count (anemia), all of which can cause lower than normal blood pressure.

• Electrocardiogram (ECG). During this painless, noninvasive test, soft, sticky patches (electrodes) are attached to the skin of your chest, arms and legs. The patches detect your heart's electrical signals while a machine records them on graph paper or displays them on a screen.
  An ECG, which can be performed in your doctor's office, detects irregularities in your heart rhythm, structural problems in your heart, and problems with the supply of blood and oxygen to your heart muscle. It can also tell if you're having a heart attack or have had one in the past.

• Tilt table test. If you have low blood pressure on standing or from faulty brain signals (neurally mediated hypotension), a tilt table test can evaluate how your body reacts to changes in position.
  During the test, you lie on a table that's tilted to raise the upper part of your body, which simulates the movement from horizontal to a standing position.

Treatment

Compression stockings

Low blood pressure that either doesn't cause signs or symptoms or causes only mild symptoms rarely requires treatment.

If you have symptoms, treatment depends on the cause. For instance, when medication causes low blood pressure, treatment usually involves changing or stopping the medication or lowering the dose.

If it's not clear what's causing low blood pressure or no treatment exists, the goal is to raise your blood pressure and reduce signs and symptoms. Depending on your age, health and the type of low blood pressure you have, you can do this in several ways:

• Use more salt. Experts usually recommend limiting salt in your diet because sodium can raise blood pressure, sometimes dramatically. For people with low blood pressure, that can be a good thing.
  But because excess sodium can lead to heart failure, especially in older adults, it's important to check with your doctor before increasing the salt in your diet.

• Drink more water. Fluids increase blood volume and help prevent dehydration, both of which are important in treating hypotension.

• Wear compression stockings. The elastic stockings commonly used to relieve the pain and swelling of varicose veins can help reduce the pooling of blood in your legs.
  Some people tolerate elastic abdominal binders better than they do compression stockings.

• Medications. Several medications can be used to treat low blood pressure that occurs when you stand up (orthostatic hypotension). 

Lifestyle and home remedies

Depending on the reason for your low blood pressure, you might be able to reduce or prevent symptoms.

• Drink more water, less alcohol. Alcohol is dehydrating and can lower blood pressure, even if you drink in moderation. Water, on the other hand, fights dehydration and increases blood volume.

• Pay attention to your body positions. Gently move from a prone or squatting to a standing position. Don't sit with your legs crossed.
  If you begin to get symptoms while standing, cross your thighs in a scissors fashion and squeeze, or put one foot on a ledge or chair and lean as far forward as possible. These moves encourage blood flow from your legs to your heart.

• Eat small, low-carb meals. To help prevent blood pressure from dropping sharply after meals, eat small portions several times a day and limit high-carbohydrate foods such as potatoes, rice, pasta and bread.
  Your doctor also might recommend drinking one or two strong cups of caffeinated coffee or tea with breakfast. Don't drink caffeine throughout the day because you will become less sensitive to caffeine, and caffeine can cause dehydration.

• Exercise regularly. Aim for 30 to 60 minutes a day of exercise that raises your heart rate and resistance exercises two or three days a week. Avoid exercising in hot, humid conditions.