Low Blood Pressure Causes, Symptoms, Treatment

Low blood pressure is also known as hypotension and is usually diagnosed with a blood pressure reading that is consistently lower than 90/60 mm/Hg. 

Some people have naturally low blood pressure, which doesn’t cause any symptoms. However, if the blood pressure is too low, it can affect blood flow around the body making a person feel dizzy or unsteady. Sudden drops in blood pressure most commonly occur in someone who’s rising from a prone or sitting position to standing. This kind of low blood pressure is known as postural hypotension, orthostatic hypotension, or neurally mediated orthostatic hypotension. Postural hypotension is considered a failure of the autonomic nervous system – the part of the nervous system that controls involuntary vital actions, such as heartbeat – to react appropriately to sudden changes. Normally, when you stand up, some blood pools in your lower extremities. Uncorrected, this would cause your blood pressure to fall. But your body normally compensates by sending messages to your heart to beat faster and to your blood vessels to constrict. This offsets the drop in blood pressure. If this does not happen, or happens too slowly, postural hypotension results.

Hypotension

The risk of both low and high blood pressure normally increases with age, due in part to normal changes during ageing. In addition, blood flow in the brain declines with age, often as a result of plaque build-up in blood vessels. An estimated 10 to 20% of people over age 65 have postural hypotension.

What causes low blood pressure?

The cause of low blood pressure isn’t always clear. It may be associated with the following:

  • Pregnancy
  • Hormonal problems, such as an underactive thyroid (hypothyroidism), overactive thyroid (hyperthyroidism), diabetes, or low blood sugar (hypoglycemia)
  • Over-the-counter medication
  • Overdose of high blood pressure medication
  • Heart failure
  • Heart arrhythmias (abnormal heart rhythms)
  • Widening, or dilation, of the blood vessels
  • Heat exhaustion or heat stroke
  • Liver disease

What causes a sudden drop in blood pressure?

Sudden drops in blood pressure can be life-threatening. Causes of this type of hypotension include:

  • Loss of blood from bleeding
  • Low body temperature
  • High body temperature
  • Heart muscle disease causing heart failure
  • Sepsis, a severe blood infection
  • Severe dehydration from vomiting, diarrhoea, or high temperature
  • A reaction to medication or alcohol
  • A severe allergic reaction, called anaphylaxis

Who gets postural hypotension?

Postural hypotension, which is low blood pressure when standing up suddenly, can happen to anyone for a variety of reasons, such as dehydration, lack of food, prolonged time in the heat, or being overly fatigued. It can also be influenced by genetic make-up, ageing, medication, dietary and psychological factors, and acute triggers, such as infection and allergy.

Postural hypotension occurs most frequently in people who are taking drugs to control high blood pressure (hypertension). It can also be related to pregnancy, strong emotions, narrowing of the arteries ( atherosclerosis), or diabetes. Elderly people are particularly affected, especially those who have high blood pressure or autonomic nervous system dysfunction.

Hypotension after meals is a common cause of dizziness and falls after eating. It’s believed to be caused by blood pooling into the vessels of the stomach and intestines.

Several drugs are commonly associated with postural hypotension. These medications can be divided into two major categories:

Drugs used to treat high blood pressure, such as diuretics, beta-blockers, calcium-channel blockers, and angiotensin-converting enzyme (ACE) inhibitors.

Drugs that have hypotension as a side effect, including nitrates, drugs for Parkinson’s disease, antipsychotics, neuroleptics, anti- anxiety agents, sedative-hypnotics, and tricyclic antidepressants.

Common causes of naturally occurring postural hypotension include:

Dehydration and electrolyte loss, which may result from diarrhoea, vomiting, excessive blood loss during menstruation, or other conditions

Age-associated decline in blood pressure regulation, which may be worsened by certain health conditions or medications

Certain diseases can cause postural hypotension.

Common causes of pathologic (attributable to a disease) postural hypotension include:

Central nervous system disorders, such as Shy-Drager syndrome or multiple system atrophy

Nerve problems, such as peripheral neuropathy or autonomic neuropathy

Cardiovascular disorders

Alcoholism

Nutritional diseases

Less common diseases that can cause postural hypotension include amyloidosis (caused by deposits of a waxy substance called amyloid in the body), vitamin deficiencies, spinal cord injuries, and neuropathies associated with cancer, particularly lung cancer or pancreatic cancer.

How do I know if I have low blood pressure?

Your doctor can diagnose you with low blood pressure. Symptoms of dizziness and light-headedness when you stand up don’t necessarily mean that you have postural hypotension, or low blood pressure. A wide range of underlying conditions may cause your symptoms. It is important to identify the cause of low blood pressure so appropriate treatment can be given.

Your doctor will look at your medical history, age, specific symptoms, and the conditions under which the symptoms occurred. He or she may perform repeated evaluation of your blood pressure and pulse rate -after you’ve been lying down for a few minutes and within two to five minutes after you stand quietly.

Other tests may be performed, such as an ECG ( electrocardiogram) to measure heart rate and rhythm and an echocardiogram (an ultrasound test to visualise the heart). You may also have blood tests to look for anaemia or problems with your blood sugar levels.

More sophisticated home ECG monitoring (a Holter monitor or “event” monitor) may be necessary to check for heart problems that occur intermittently.

An exercise stress test or electrophysiology test (EP test) may also be helpful.

Serious forms of postural hypotension may require a test called a ‘tilt table’ test. This test evaluates the body’s reaction to position and changes in position. The person lies on a table, is safely strapped in, and the table is raised to an upright position for up to an hour. Blood pressure, heart rate, and symptoms are recorded. Often, medications are given to help guide treatment.

What are the symptoms of low blood pressure?

  • Dizziness
  • Lightheadedness
  • Unsteadiness
  • Dimming or blurring of vision
  • Weakness
  • Fatigue
  • Confusion
  • Chest pain
  • Cold, clammy skin
  • Fainting
  • Breathing difficulty
  • When to seek medical advice

Seek medical care immediately if you experience any of the above signs of low blood pressure.

Seek medical advice if you experience an increased frequency of symptoms of low blood pressure that are interfering with your lifestyle, that pose a risk of injury from falling, or that you suspect may be a side effect of prescription or nonprescription medication.

If your blood pressure gets severely low, there’s a significant danger that your body will not receive enough oxygen to carry out its normal functions. Decreased oxygen can result in impaired functioning of the heart and brain and cause difficulty with breathing. Someone with low blood pressure can lose consciousness or go into shock (when the organs shut down).

What are the treatments for low blood pressure?

If you have an underlying medical problem that causes low blood pressure, seek treatment for the underlying condition. For many people, chronic low blood pressure can be effectively treated with diet and lifestyle changes.

Initially, your doctor may advise you to increase your blood pressure by making these simple changes:

Eat a diet higher in salt.

Increase or decrease your intake of caffeine depending on individual medical advice.

Drink lots of non-alcoholic fluids — a minimum of eight glasses per day. Sports drinks that are high in sodium and potassium may be recommended, especially during exercise or in hot weather.

Drink more fluids during hot weather and while sick with a viral illness, such as a cold or the flu.

Have your doctor evaluate your prescription and over-the-counter medications to identify any that may be causing your symptoms.

Get regular exercise to promote blood flow.

Be careful when rising from a lying down or sitting position. To improve circulation, pump your feet and ankles a few times before standing up. Then proceed slowly. When getting out of bed, sit upright on the edge of the bed for a few minutes before standing.

Elevate the head of your bed at night by five to 20 degrees, by placing bricks or blocks under the head of bed.

Avoid heavy lifting.

Avoid straining while on the toilet.

Avoid prolonged exposure to hot water, such as hot showers and spas. If you get dizzy, sit down. It may be helpful to keep a chair or stool in the shower in case you need to sit; to help prevent injury, use a nonslip chair or stool designed for use in showers and bath tubs.

To avoid problems with low blood pressure and lessen episodes of dizziness after meals, try eating smaller, more frequent meals. Rest after eating. Avoid taking low blood pressure drugs before meals.

If needed, use elastic support (compression) stockings or tights that cover the calf and thigh. These may help restrict pooling of blood in the legs, thus keeping blood moving as it should do.

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