Low blood pressure (hypotension)

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 or surgical 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 (syncope)
Blurred 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 indications of shock, seek emergency medical help.

If you have consistently low blood pressure readings but feel fine, your doctor is likely just to 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 hypotension 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 generates 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.

Throughout the day, blood pressure varies, depending on body position, breathing rhythm, stress level, physical condition, medications you take, what you eat and drink, and 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 an adequate supply of blood. And big plunges, 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. Thyroid conditions such as 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 diarrhea, 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 vitamins B-12 and folate 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 (Maxzide, 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, Cialis), particularly when taken with the heart medication nitroglycerin

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.

It's also possible to have delayed orthostatic hypotension, with signs and symptoms developing 5 to 10 minutes after a change in posture. This might be a milder form of the condition, or it could be an early stage of it.

Low blood pressure after eating (postprandial hypotension). This sudden drop in blood pressure after eating 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.

Lowering the dose of blood pressure drugs and eating small, low-carbohydrate meals 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 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 normal functions, leading to damage to your heart and brain.

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High blood pressure (hypertension)

Overview

High blood pressure 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.

You can have high blood pressure (hypertension) for years without any symptoms. Even without symptoms, damage to blood vessels and your heart continues and can be detected. Uncontrolled high blood pressure increases your risk of serious health problems, including heart attack and stroke.

High blood pressure generally develops over many years, and it affects nearly everyone eventually. 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.

Blood pressure generally should be checked in both arms to determine if there's a difference. It's important to use an appropriate-sized arm cuff.

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.

If you don't regularly see your doctor, you may be able to get a free blood pressure screening at a health resource fair or other locations in your community. You can also find machines in some stores that will measure your blood pressure for free.

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. Ask your doctor for advice on using public blood pressure 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 problems
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 volume of blood circulated 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. If you don't get enough potassium in your diet or retain enough potassium, you may accumulate too much sodium 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. If you try to relax by eating more, using tobacco or drinking alcohol, you may only increase problems with high blood pressure.
Certain chronic conditions. Certain chronic conditions also may increase your risk of high blood pressure, such as 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, obesity 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 organs in your body. 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 cluster of disorders of your body's metabolism, including increased waist circumference; high triglycerides; low 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.

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