Hypotension

Low blood pressure, also known as hypotension, occurs when blood flows through your blood vessels at lower than normal pressures. While many people have naturally low blood pressure without problems, sometimes it can signal an underlying health issue or cause troubling symptoms like dizziness and fainting.

Table of contents

• What is hypotension?
• Types of low blood pressure
• Symptoms
• Causes
• Diagnosis
• Treatment
• Managing symptoms at home
• When to seek medical help

What is hypotension?

Blood pressure measures the force of blood pushing against the walls of your arteries as your heart pumps blood throughout your body^[1]. It is recorded as two numbers: the first number, called systolic pressure, measures the pressure when your heart beats. The second number, called diastolic pressure, measures the pressure when your heart rests between beats^[2]. Both numbers are measured in millimeters of mercury, written as mm Hg.

Normal blood pressure typically ranges from 90/60 to 120/80 mm Hg^[3]. Low blood pressure is generally defined as a reading lower than 90/60 mm Hg^[1]. However, what counts as low can vary from person to person. Some people naturally have lower blood pressure and feel perfectly healthy. Low blood pressure only becomes a concern when it causes symptoms or indicates an underlying health problem^[8].

For many people, hypotension doesn’t cause any symptoms at all. Many don’t even know their blood pressure is low unless they measure it^[2]. When blood pressure is too low, vital organs like the heart, brain, and lungs may not receive enough blood and oxygen^[7].

Types of low blood pressure

There are several types of hypotension, each with different triggers and patterns^[1].

Orthostatic hypotension, also called postural hypotension, is a sudden drop in blood pressure when you stand up after sitting or lying down^[1]. This type happens when your cardiovascular or nervous system doesn’t react appropriately to sudden position changes^[8]. It’s defined as a decrease in systolic pressure of at least 20 mm Hg or a decrease in diastolic pressure of at least 10 mm Hg within three minutes of standing^[16]. This form is common in older adults, affecting an estimated 5% of people at age 50 and climbing to more than 30% in people over 70^[2].

Postprandial hypotension occurs one to two hours after eating^[1]. Blood pools into the vessels of the stomach and intestines after a meal, causing blood pressure to drop^[8]. This type most often affects older adults, especially those with high blood pressure or conditions affecting the autonomic nervous system (the part of your nervous system that controls automatic functions like breathing and heart rate), such as Parkinson’s disease^[1]. It tends to happen after large meals containing lots of carbohydrates^[8].

Neurally mediated hypotension is a blood pressure drop that happens after standing for long periods of time^[1]. It’s thought to occur because of communication problems between your brain and your heart^[8]. This type is more common in younger people and children usually outgrow it^[7].

Multiple system atrophy with orthostatic hypotension is a rare type of low blood pressure that happens when you’re lying down^[8]. It involves your involuntary nervous system, which controls functions like blood pressure, breathing, and heart rate.

Symptoms

Low blood pressure symptoms can vary depending on how quickly it develops and what’s causing it^[2]. Slow decreases in blood pressure happen normally as people age, while fast decreases can mean certain parts of your body aren’t getting enough blood flow^[2].

Common symptoms include dizziness or feeling lightheaded, especially when standing up^[2]. You might experience fainting or passing out, which doctors call syncope^[2]. Other symptoms include nausea or vomiting, distorted or blurred vision, and fast, shallow breathing^[2].

You may also feel fatigue or weakness, feel tired, sluggish or lethargic, or have confusion or trouble concentrating^[2]. Some people experience unusual changes in behavior, not acting like themselves^[2]. Additional symptoms can include feeling sick, generally feeling weak, and having cold, clammy skin^[5].

Decreased cerebral perfusion, meaning reduced blood flow to the brain, produces the neurologic symptoms of orthostatic hypotension^[16]. Usually, your body can automatically control your blood pressure and keep it from dropping too much by speeding up your heart rate or making blood vessels narrower. Symptoms happen when your body can’t offset the drop in blood pressure^[2].

Causes

Many factors can cause low blood pressure. The cause isn’t always clear, but several health conditions and situations are commonly linked to hypotension^[8].

Dehydration, which occurs when your body loses too much fluid, reduces blood volume and can lower blood pressure^[1]. Blood loss from an injury can cause a sudden drop in blood pressure^[7]. Internal bleeding, such as from a perforated stomach ulcer, or blood loss from trauma like a road accident or deep cut can also lead to hypotension^[5].

Various heart problems can cause low blood pressure. These include heart failure, arrhythmias (irregular heartbeat), and heart valve disease^[7]. An extremely low heart rate, called bradycardia, can prevent the heart from pumping blood effectively^[9]. Heart attack can also lower blood pressure^[9].

Problems with the autonomic nervous system can lead to hypotension^[7]. Nerve damage from diabetes or other disorders can affect blood pressure control^[7]. Some nervous system disorders, such as Parkinson’s disease, can cause low blood pressure^[1].

Certain medical conditions affect blood pressure. Disorders of the endocrine system, such as adrenal insufficiency (Addison’s disease) or low thyroid function (hypothyroidism), may cause hypotension^[2]. Severe infection, called septicemia, can cause blood infection and inflammation that affects blood vessels, leading to low blood pressure^[2]. A severe allergic reaction called anaphylaxis can also cause a sudden, dangerous drop in blood pressure^[9].

Pregnancy commonly causes blood pressure changes^[8]. Emotional stress, fear, insecurity or pain are among the most common causes of fainting related to low blood pressure^[5].

Many medications can lead to low blood pressure as a side effect^[7]. These include medicines used to treat high blood pressure, depression, or Parkinson’s disease^[7]. Diuretics, which help your body get rid of extra fluid, are a common culprit^[23]. Drugs that lower blood pressure by relaxing blood vessels, such as beta blockers and calcium-channel blockers, can also be problematic^[23]. Other medications that may contribute include some over-the-counter medicines, drugs for an enlarged prostate, erectile dysfunction medications, and certain antidepressants^[23].

Some forms of infection, such as toxic shock syndrome, can cause low blood pressure^[5]. Being on bed rest for long periods can also lead to hypotension^[8]. Older adults have a higher risk for symptoms of low blood pressure, such as falling, fainting, or dizziness upon standing up or after a meal^[7].

Diagnosis

To diagnose hypotension, your healthcare provider will give you a physical exam and ask questions about your medical history^[18]. They will want to know about your general health, family history, lifestyle, and what medicines you take^[9]. The exam includes checking your blood pressure^[1].

You can check your blood pressure in several ways: by asking a pharmacist to do it, by asking a practice nurse or doctor to do it, or at home yourself using a home blood pressure monitor^[6]. If you’re 40 to 74 years old, you should have your blood pressure checked at least once every five years as part of regular health screening^[6].

Your healthcare provider will measure your blood pressure while you’re sitting or lying down, and then again while standing. This helps identify orthostatic hypotension^[16]. Your vital signs, including temperature, pulse, rate of breathing, and blood pressure, will be checked frequently^[17].

If standard blood pressure measurements don’t show clear results but you have symptoms of orthostatic hypotension, or if you can’t stand for measurements, your provider may recommend a tilt table test^[1]. During this test, you begin by lying flat on a table. Straps hold you in place. After lying flat for a while, the table is tilted to a position that mimics standing^[18]. The healthcare professional watches how your heart and the nervous system that controls it respond to the changes in position^[18]. The test is done at an angle of at least 60 degrees^[16].

Various tests may be done to find out the cause of your low blood pressure^[17]. Blood tests can help find conditions that can lower blood pressure, such as low blood sugar (hypoglycemia), high blood sugar (diabetes), and a low red blood cell count (anemia)^[18]. An electrocardiogram (ECG or EKG) measures the electrical activity of your heart^[18]. Other tests might include a complete blood count, blood cultures to check for infection, or a urinalysis^[17].

Treatment

Treatment for low blood pressure depends on what’s causing it and whether you have symptoms^[6]. Lower than normal blood pressure in a healthy person that doesn’t cause any symptoms often doesn’t need treatment^[17].

If a cause for low blood pressure can be found, your doctor will be able to recommend treatment to ease your symptoms^[6]. The first step is often reviewing and adjusting medications. If medicines are the cause, your provider may change the dosage or switch you to a different medicine^[6]. Because there are so many different blood pressure drugs, just changing from one class of drugs to another can help^[23]. You should not stop taking any medicines before talking to your provider^[6].

For dehydration, your provider may suggest drinking more fluids^[6]. Treatment might include correcting reversible causes and discontinuing responsible medications when possible^[3].

Wearing support stockings, also called compression stockings, can improve circulation and increase blood pressure^[6]. These stockings help keep blood from collecting in the legs, which keeps more blood in the upper body^[17].

Medicine to increase blood pressure is rarely needed because simple lifestyle measures or treating the underlying cause is usually effective^[6]. However, for patients who don’t respond adequately to non-drug treatments, certain medications have proven beneficial^[3]. These include fludrocortisone, midodrine, and pyridostigmine^[3].

Severe hypotension caused by shock is a medical emergency^[17]. You may be given blood or other fluids through a needle, medicines to increase blood pressure and improve heart strength, or other medicines such as antibiotics^[17].

Managing symptoms at home

There are several things you can do to help with symptoms of low blood pressure^[6]. These lifestyle changes are often effective and should be offered to all patients^[3].

When changing positions, move slowly. Get up slowly from sitting to standing^[6]. Take care when getting out of bed by moving slowly from lying to sitting to standing^[6]. Try stretching out of bed to get the blood flowing around your body before you move to a sitting position, then stand slowly^[19]. When getting up from sitting, cross and uncross your legs a few times before standing up^[19].

Sleeping with your head elevated can also help^[19]. To do this, you’ll need to lift your bed so the top end, where your pillow sits, is higher than the bottom. You can do this with extra pillows under your head or by placing wedges under the mattress or bed legs^[19].

If you sit or stand for long periods, try to move more^[19]. Staying still for too long, such as sitting in a chair to watch TV or when working at a desk, can cause blood pressure to fall^[19]. Don’t sit or stand for long periods, and don’t bend down or change posture suddenly^[6].

Eat small, frequent meals rather than large ones^[6]. Lying down or sitting still for a while after eating may also help^[6]. Patients with chronic orthostatic hypotension should be counseled to avoid large carbohydrate-rich meals^[3].

Increase the amount of water you drink^[6]. Drinking plenty of fluids and choosing water and other clear liquids helps^[21]. If you have kidney, heart, or liver disease and have to limit fluids, talk with your doctor before you increase the amount of fluids you drink^[21]. Your provider may also suggest adding more salt to your diet if recommended^[21]. Patients should ensure adequate hydration and limit alcohol intake^[3]. Don’t drink too much alcohol^[6].

If you feel dizzy or lightheaded, sit down or lie down for a few minutes^[21]. When you have symptoms from low blood pressure, sit or lie down right away, then raise your feet above heart level^[17]. You can also sit down and put your head between your knees^[21]. This will help your blood pressure go back to normal and help your symptoms go away.

When to seek medical help

You should see a doctor if you keep getting symptoms of low blood pressure such as dizziness and fainting^[6]. Get your blood pressure checked if you keep experiencing lightheadedness or dizziness, feeling sick, blurred vision, generally feeling weak, confusion, or fainting^[6].

Call emergency services immediately if someone collapses^[9]. You should also call for emergency care anytime you think you may need it, such as if you passed out or lost consciousness^[21].

Call your doctor or seek immediate medical care if you are dizzy or lightheaded, or you feel like you may faint^[21]. You should seek care if you have dizziness, fainting, lightheadedness, blurred vision, palpitations, confusion, nausea or general weakness^[24]. It’s important to seek care if your symptoms make it hard to do your daily activities or affect your quality of life^[24].

Watch closely for changes in your health, and be sure to contact your doctor if you have any problems^[21].