1 What is Low Blood Pressure (Hypotension)?

Low blood pressure is a condition, medically termed as hypotension, which occurs when your blood pressure significantly drops much lower than the normal reading. This results in insufficient blood supply to your heart, brain, and other parts of your body.

Normal blood pressure ranges between 90/60 mmHg and 120/80 mmHg.

Although blood pressure varies among individuals, a blood pressure reading of 90 millimeters of mercury (mm Hg) or less systolic blood pressure (the top number in a blood pressure reading) or 60 mm Hg or less diastolic blood pressure (the bottom number) is generally considered as low blood pressure.

In most people, low blood pressure may cause symptoms such as fainting and dizziness. The causative factors of low blood pressure ranges from dehydration to severe medical and surgical conditions.

It is a treatable condition, but identifying the exact cause is important so that the condition can be treated appropriately. Severe cases of low blood pressure can sometimes be fatal.

2 Symptoms

Low blood pressure is accompanied by signs and symptoms such as:

  • Dizziness or light-headedness
  • Fainting (syncope)
  • Confusion or lack of concentration
  • Blurry vision
  • Nausea and vomiting
  • Feeling of thirst
  • Cold, clammy, pale skin
  • Rapid, shallow breathing
  • Sleepiness
  • Weakness or fatigue
  • Depression

Low blood pressure, in some people, may be an indicator of an underlying problem, particularly, when blood pressure drops suddenly.

When to see a doctor?

In most cases, low blood pressure is not a serious problem. If you have consistently low blood pressure, but feel fine, your doctor will monitor you during routine exams.

Occasional dizziness or lightheadedness is a relatively minor problem, and may be a result of mild dehydration that occurs from being exposed to the sun for too much time or a hot tub. In these situations, how quickly your blood pressure drops is a matter of concern, but not how low it goes.

However, it is very important to see your doctor if you experience signs or symptoms related to hypotension because they can sometimes point to more-serious underlying problems. You should keep a record of your symptoms, when they occur, and what you were doing at that time.

3 Causes

The cause of hypotension varies from person to person, so it is important to discuss with your doctor to find the exact underlying cause.

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

Here's what the numbers indicate:

  • Systolic pressure: The first (top) number in a blood pressure reading, this reveals the amount of pressure your heart generates when pumping blood through your arteries into the rest of your body.
  • Diastolic pressure: The second (bottom) number in a blood pressure reading refers to the amount of pressure in your arteries when your heart is resting in between beats.

Blood pressure is not always the same, though you can get an accurate blood pressure reading at any given time, and it varies from one person to another. It may vary considerably in a short amount of time — sometimes from one heartbeat to the next, depending on your body position, breathing rhythm, stress levels, physical condition, your medications, what you eat and drink, and even time of day.

Blood pressure is usually lowest while you sleep during the night and rises sharply on waking up in the morning. A drop in blood pressure as little as 20 mmHg can cause symptoms in some people.

Blood pressure: How low can you go?

What is considered low blood pressure for you may still be normal for someone else. Most doctors term chronically low blood pressure too low only if it gives rise to noticeable symptoms.

Some experts define low blood pressure as readings lower than 90 mm Hg systolic or 60 mm Hg diastolic. If any one number is in the lower range, your blood pressure is considered to be lower than normal.

In other words, if your systolic pressure is 115, but your diastolic pressure is 50, you are still considered to have low blood pressure.

A sudden drop in blood pressure also can be very dangerous. Sometimes, even a drop of just 20 mm Hg — from 110 systolic to 90 mm Hg systolic — can cause dizziness and fainting as your brain is deprived of an adequate supply of blood.

Big plunges, especially caused due to uncontrolled bleeding, severe infections or allergic reactions are life-threatening. Athletes and people who exercise regularly have lower blood pressure and a slower heart rate than do people who are not so fit.

Generally, nonsmokers and people who follow a healthy diet and maintain a normal weight may have their blood pressure lower than normal. In some rare instances, low blood pressure can be a sign of serious life-threatening disorders.

Conditions that can cause low blood pressure

Some medical conditions can cause low blood pressure. These include:

  • Pregnancy: Blood pressure may drop during pregnancy as a woman's circulatory system expands rapidly during this phase. This is absolutely normal, and blood pressure returns to your pre-pregnancy level after giving birth.
  • Heart conditions: Some heart disorders that can lead to low blood pressure include extremely low heart rate (bradycardia), heart valve diseases, heart attack, and heart failure. These conditions lead to low blood pressure because they prevent your body from being able to circulate enough blood. 
  • 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. 
  • Not drinking enough fluids (dehydration): When you become dehydrated, your body tend to lose more water than you drink. Even mild dehydration can cause weakness, dizziness, and fatigue. Fever, vomiting, severe diarrhea, overuse of diuretics, and performing strenuous exercises can lead to dehydration. Even more serious is hypovolemic shock, a life-threatening complication of dehydration. It occurs when low blood volume results in a sudden drop of blood pressure and a decrease in the amount of oxygen reaching your tissues. If left untreated, severe hypovolemic shock can result in death within a few minutes to hours. 
  • Sudden loss of blood (shock): A major injury or internal bleeding may result in loss of large amounts of blood, which reduces your blood volume, leading to a severe drop in blood pressure. 
  • Severe infection (septicemia): Septicemia develops when an infection in the body gains entry into the bloodstream. This condition leads to a fatal drop in blood pressure called septic shock. 
  • Severe allergic reaction (anaphylaxis): Anaphylaxis is a serious and potentially life-threatening allergic reaction. Common triggering factors of anaphylaxis include certain foods, medications, insect venoms, and latex. Anaphylaxis can result in breathing difficulty, hives, itching, a swollen throat, and a fall in blood pressure. 
  • A diet deficient in nutrients: A deficiency of vitamins B12 and folate can cause a condition in which your body does not produce enough red blood cells (anemia), which in turn causes low blood pressure. 

Medications that can cause low blood pressure

Some medications you may take can also cause low blood pressure, including:

  • Diuretics (water pills), such as furosemide (Lasix) and hydrochlorothiazide (Microzide, Oretic)
  • Alpha blockers, such as prazosin (Minipress) and labetalol 
  • Beta blockers, such as atenolol (Tenormin), propranolol (Inderal, Innopran XL, others) and timolol 
  • Drugs for Parkinson's disease, such as pramipexole (Mirapex) or those containing levodopa 
  • Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor), imipramine (Tofranil), protriptyline (Vivactil) and trimipramine (Surmontil)
  • Sildenafil (Viagra) or tadalafil (Cialis), particularly in combination with the heart medication nitroglycerin

Types of low blood pressure

Doctors often divide low blood pressure (hypotension) into different categories, based on their 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 that most often occurs when you stand up from a sitting position or if you stand up after lying down for some time. This type of low blood pressure often lasts for only a few seconds or minutes.

    Naturally, gravity causes blood to collect in your legs whenever you stand. Your body normally compensates for this phenomenon by raising your heart rate and constricting blood vessels, so that enough blood returns to your brain. But, in people with orthostatic hypotension, there is a failure in this compensatory mechanism causing blood pressure to drop leading to symptoms such as dizziness, lightheadedness, blurred vision, and even fainting.

    Orthostatic hypotension can occur for a variety of 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 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 very common in older adults, with as many as 20 percent of elderly people above the age of 65 experience orthostatic hypotension. Orthostatic hypotension may also occur in young, otherwise healthy people who try to quickly stand up after sitting with their legs crossed for prolonged periods or after working for a time in a squatting position.

  • Low blood pressure after eating (postprandial hypotension): Postprandial hypotension is a sudden drop in blood pressure soon after eating. It affects mostly older adults with high blood pressure or people with Parkinson's disease. Just as gravity tends to attract blood towards your feet when you stand, a large amount of blood flows to your digestive tract soon after you eat.

    Normally, your body has a compensatory mechanism that counteracts this by increasing your heart rate and constricting certain blood vessels to help maintain normal blood pressure. But, in some people these mechanisms do not occur leading to dizziness, faintness, and falls. Reducing the dose of blood pressure drugs and eating small, low-carbohydrate meals may help alleviate these symptoms.

  • Low blood pressure from faulty brain signals (neurally mediated hypotension): This disorder causes blood pressure to drop after standing for a long time, leading to signs and symptoms such as dizziness, nausea and fainting.

    Neurally mediated hypotension most commonly affects young adults and children, and it seems to occur as a result of a miscommunication between the heart and the brain. Usually, children outgrow this type of hypotension.

    When you stand for a prolonged period, your blood pressure falls as blood collects in your legs. Normally, your body makes adjustments to normalize your blood pressure. But, in people with neurally mediated hypotension, nerves in the heart's left ventricle actually signal the brain that blood pressure is too high, rather than too low. As a result, the brain decreases the heart rate, reducing your blood pressure even further. This causes even more blood to pool in your legs, and less blood reaches your brain leading to lightheadedness and fainting.

  • Low blood pressure due to nervous system damage (multiple system atrophy with orthostatic hypotension): This condition is also called Shy-Drager syndrome. Although, this condition is associated with muscle tremors, slow movements, problems with coordination and speech, and incontinence, its main characteristic is severe orthostatic hypotension in combination with very high blood pressure when lying down.

4 Making a Diagnosis

Testing for low blood pressure helps to find and diagnose the underlying cause.

No special preparations need to be done to have your blood pressure checked. You may wear a short-sleeved shirt to your appointment so that the blood pressure cuff can be fitted around your arm properly. Do not discontinue any prescription medications that you think may affect your blood pressure unless your doctor has directed.

As your appointments are going to be brief, and there is often a lot to discuss, it is a good idea to be prepared for your appointment. Here is some information to help you get ready for your appointment.

What you can do?

  • At the time you schedule the appointment, be sure to ask if there is anything you need to know in advance, such as dietary restrictions before undergoing a blood test.
  • Write down all the symptoms you are experiencing, including those that seem unrelated to low blood pressure. 
  • Write down key personal information, including a family history of low blood pressure and any major stresses or recent life changes. 
  • Make a list of regular medications, vitamins or supplements that you take. 
  • Ask a family member or friend along, if possible. Sometimes, it can be difficult to remember all the information provided to you during an appointment. Someone who accompanies you might remember something that you missed or forgot. 
  • Be prepared to discuss your diet and exercise habits. If you do not have a diet or exercise routine already, be ready to talk to your doctor about any challenges you might face in getting started.
  • Write down questions to ask your doctor..
  • Preparing a list of questions will help you make the most of your time together. For low blood pressure, some basic questions to ask your doctor include:
    • What is the most likely cause of my symptoms or condition? 
    • What are other possible causes of my symptoms or condition? 
    • What kind of tests do I need?
    • What is the most suitable treatment? 
    • What type of foods should I eat or avoid?
    • What is an appropriate level of physical activity for me? 
    • How often should I have follow-up checkups for low blood pressure?
    • How can I best manage my other conditions together? 
    • Should any restrictions be followed? 
    • Is there any generic alternative to the medicine you have prescribed? 
    • Are there any brochures or other printed materials that I can take home? What websites do you recommend visiting?

What to expect from your doctor ?

Your doctor will ask you a number of questions. Be ready to answer them and reserve time to discuss the points you want to spend more time on.

Your doctor may ask:

  • When did you begin experiencing your symptoms first?
  • Have your symptoms been continuous or occasional? 
  • How severe are your symptoms? 
  • Do you feel dizzy or light-headed while standing or sitting after lying down?
  • What, if anything, seems to improve or worsen your symptoms? 
  • Have you been diagnosed with any other health conditions? 
  • Have you had any recent illness, accident, or injury?
  • What medications do you take currently? 
  • What is your typical daily diet? 
  • How much exercise do you get in an average week? 
  • Do you have a family history of heart disease?

Your doctor will examine you to determine the cause of your low blood pressure. The goal of testing for low blood pressure is to find out the underlying cause.

This helps to determine the most appropriate treatment and identify any heart, brain or nervous system problems that is causing your lower than normal readings. Your vital signs (temperature, pulse, rate of breathing, and blood pressure) will be checked frequently. 

To make a diagnosis, your doctor may order one or more of the following tests:

  •  Blood pressure test: Your blood pressure reading is taken by using an inflatable arm cuff and a pressure-measuring gauge. A blood pressure reading, given in millimeters of mercury (mm Hg), has two numbers. The first, or upper, number measures the pressure in your arteries when your heart beats (systolic pressure). The second, or lower, number measures the pressure in your arteries between beats (diastolic pressure).
  • Blood tests: These tests provide information regarding your overall health as well as whether you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia or diabetes) or a low number of red blood cells (anemia), all of which can cause lower than normal blood pressure. 
  • Electrocardiogram (ECG): This is a painless, noninvasive test in which soft, sticky patches called electrodes are fixed on to the skin of your chest, arms, and legs. These patches can detect your heart's electrical signals, which is recorded on graph paper with a machine or displayed on a screen.

    An ECG can be performed in your doctor's office, and can detect irregularities in your heart rhythm, structural abnormalities in your heart, and problems with the blood supply to your heart muscle. It can also detect if you are prone to have a heart attack or whether you have had a heart attack earlier.

    Sometimes, heart rhythm abnormalities are transient in nature, and an ECG will not be able to find any problems. In such cases, you may be advised to wear a 24-hour Holter monitor that records your heart's electrical activity as you perform your daily routine activities.

  • Echocardiogram: This is a noninvasive test in which an ultrasound of your chest area is done. This shows detailed pictures of your heart's structure and function.

    Ultrasound waves are transmitted, and their echoes are recorded using a device called a transducer, which is placed outside your body. A computer uses this information from the transducer to create moving images, which is displayed on a video monitor. 

  • Stress test: Certain heart disorders that cause low blood pressure are more easily diagnosed when your heart is working harder than when it is at rest. During a stress test, you will be asked to exercise, such as walking on a treadmill.

    Sometimes, if you are not able to exercise, you may be given a medication to make your heart work harder. While your heart is working harder, your heart will be monitored using electrocardiography or echocardiography. Your blood pressure may also be monitored.

  • Valsalva maneuver: This is a noninvasive test that checks the functioning of your autonomic nervous system by performing an analysis of your heart rate and blood pressure following several cycles of a type of deep breathing: You will be asked to take a deep breath and then force the air out through your lips, as if you were trying to blow up a stiff balloon.
  • Tilt table test: If there is low blood pressure noted on standing or from faulty brain signals (neurally mediated hypotension), your doctor may advise a tilt table test, which evaluates your body's reaction to changes in position. During this test, you will be lying down on a table that is tilted slowly to raise the upper part of your body, which simulates your movement from horizontal to a standing position.

5 Treatment

Low blood pressure that doesn't cause signs or symptoms or causes only mild symptoms, such as brief episodes of dizziness when standing, rarely requires treatment.

The most appropriate treatment is suggested based on the underlying cause of your low blood pressure, and doctors usually focus on the primary health problem – dehydration, heart failure, diabetes or hypothyroidism — rather than the low blood pressure itself.

If your low blood pressure is caused by medications, your doctor will change the dosage of your medication or stop it entirely and prescribe a different medication. You should not stop taking your medications without your doctor's advice.

People with neurally mediated hypotension are advised to avoid triggers, such as standing for a prolonged period of time. Other measures include drinking fluids and increasing the intake of salt in your diet. In severe cases, medicines will be prescribed.

When you start getting symptoms of low blood pressure, you should sit or lie down immediately. Then, elevate your feet above your heart level.

If the cause of your low blood pressure remains unclear and no effective treatment exists, the goal of treatment is to provide relief from your signs and symptoms and to raise your blood pressure.

Depending on your age, overall health status, and your type of low blood pressure, this goal can be achieved in several ways:

  • Use more salt: As sodium can raise your blood pressure dramatically, experts recommend increasing the intake of salt in your diet for people with low blood pressure. But because excess amounts of sodium can also lead to heart failure, particularly in older adults, it is very important to discuss with your doctor before taking excess salt in your diet.
  • Drink more amounts of water: Fluids, especially water can increase your blood volume and help in preventing dehydration, both of which are able to treat hypotension.
  • Wear compression stockings: The elastic stockings commonly used to relieve the pain and swelling in varicose veins may help prevent the collection of blood in your legs. This holds more amount of blood in the upper portion of your body.
  • Medications: There are several medications available to treat low blood pressure that occurs when you stand up (orthostatic hypotension). These can be used either alone or together.

    For example, the drug fludrocortisone is often used in the treatment of this type of low blood pressure. This drug boosts your blood volume, which in turn raises your blood pressure.

    Doctors commonly use the drug midodrine (Orvaten) to raise the standing blood pressure levels in people with chronic orthostatic hypotension. It acts by restricting the ability of your blood vessels to expand, which raises your blood pressure.

Severe hypotension that occurs as a result of shock will be treated as a medical emergency. You may be given:

  • Blood through a needle into your vein (IV)
  • Medicines to raise blood pressure and improve heart strength
  • Other medicines, such as antibiotics

6 Prevention

Your doctor will recommend certain measures to prevent or reduce your symptoms of low blood pressure. These include:

  • Drinking plenty of fluids
  • Getting up slowly from a sitting or lying down position..
  • Avoiding alcohol consumption
  • Avoid standing for prolonged periods if you have neurally mediated hypotension..
  • Use compression stockings to prevent pooling of blood in the legs..

7 Lifestyle and Coping

You may make certain lifestyle changes to reduce or even prevent symptoms of your blood pressure, depending on the cause of your low blood pressure.

Some suggestions include:

  • Avoid drinking alcohol and drink plenty of water: Alcohol can dehydrate your body and lower your blood pressure, even if you drink in moderate amounts. Water, on the other hand, prevents dehydration and increases your blood volume.
  • Follow a healthy diet: Include a variety of foods such as whole grains, fruits, vegetables, lean meat, and fish to get all the nutrients you need for good health.
    If your doctor has advised you to use more salt, you can use natural soy sauce or add dry soup mixes to dips and dressings if you do not like a lot of salt in your food.
  • Change your body positions slowly: When you want to stand up from a prone position, do it slowly in order to reduce the dizziness and light-headedness that occurs with low blood pressure on standing. Before you rise out of your bed in the morning, take a deep breath for a few minutes, and then slowly sit up on your bed before you stand. Slightly elevate the head portion of your bed while sleeping to reduce the effects of gravity.

    If you start getting symptoms while standing, hold your thighs crossed in a scissors fashion and squeeze, or place one foot on a ledge or a chair and bend as far forwards as possible. These maneuvers encourage the flow of blood from your legs to your heart.

  • Eat small-sized, low-carbohydrate meals: Eating small amounts of food several times in a day can help in preventing blood pressure from dropping suddenly after meals. Limit the intake of high-carbohydrate foods such as potatoes, rice, pasta, and bread.

    Your doctor may also advise you to have coffee or tea along with your meals to temporarily raise your blood pressure. As caffeine can lead to other problems, check with your doctor before drinking more caffeinated beverages.

8 Risks and Complications

There are several risks and complications associated with low blood pressure (hypotension).

Low blood pressure (hypotension) can affect anyone, but there are certain types of low blood pressure that are more likely to depend on age or other risk factors.

These include:

  • Age: Sudden drop in blood pressure that occurs on standing or after eating is primarily seen in adults above the age of 65. Orthostatic, or postural, hypotension occurs after standing up, while postprandial hypotension happens after having a meal. Neurally mediated hypotension is a result of miscommunication between your brain and heart, and is more common in children and younger adults.
  • Medications: People undergoing treatment with certain high blood pressure medications, such as alpha blockers are at a greater risk of low blood pressure.
  • Certain diseases: Parkinson's disease, diabetes, and a few heart disorders can put you at a greater risk of developing low blood pressure.

Possible complications

Even moderate forms of low blood pressure can not only cause dizziness and weakness but also fainting, which results in a risk of injury from falls. Falls as a result of low blood pressure in elderly people can cause broken hip or spine fracture. These injuries can severely affect a person's quality of life and ability to move around.

Sudden, severe drop in your blood pressure due to any reason can deprive your body of sufficient oxygen to carry out its functions. This can lead to damage to your heart, brain, and other organs. This type of low blood pressure can be fatal if not treated promptly.

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