What a Sudden Drop in Blood Pressure Means

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A sudden drop in blood pressure, also called hypotension, can occur for any number of reasons. It may be due to dehydration or simply rising from your chair too quickly, causing momentary dizziness and confusion. But a sudden drop in blood pressure could also be a sign of a potentially serious condition like heart failure, heatstroke, or internal bleeding.

This article will discuss the various causes of sudden hypotension and how a sudden drop in blood pressure is diagnosed and treated. It also explains when it is time to see a healthcare provider and the signs of a medical emergency.

A woman having her blood pressure taken
Jose Luis Pelaez Inc. / Getty Images


There are many possible causes of hypotension. Some can overlap, making the diagnosis difficult in some cases. The causes can be broadly categorized as hypovolemia, decreased cardiac output, vasodilation, and hypotensive syndromes.


Hypovolemia is a term used to describe reduced blood volume. This is the most common cause of hypotension. It can occur if you are not getting enough fluids or if your body is losing too much fluid.

Common causes of hypovolemia include:


Hypovolemic shock occurs when you lose more than 20% of your blood volume for any reason. A loss at this level makes it impossible for the heart to pump a sufficient amount of blood through the body.

Decreased Cardiac Output

Even if your blood volume is normal, there are conditions that can reduce the body's ability to pump blood. This condition is known as decreased cardiac output.

It can occur as a result of a heart problem, endocrine (hormonal) dysfunction, and certain medications. Sudden changes in cardiac output can cause a sudden drop in blood pressure.

Causes of decreased cardiac output include.


Vasodilation describes the sudden widening of blood vessels. As the blood vessels get wider, blood pressure continues to drop.

Common causes of vasodilation include:

  • Vasodilating drugs: Drugs in this category include calcium channel blockers, angiotensin II receptor blockers, nitroglycerin, nitrous oxide, Rogaine (minoxidil), and Viagra (sildenafil).
  • Dysautonomia: A condition in which which the autonomic nervous system malfunctions, affecting the heart, bladder, intestines, blood vessels, and other organs
  • Sepsis: A life-threatening reaction to an infection
  • Anaphylaxis: A severe, whole-body allergy that can lead to anaphylactic shock
  • Acidosis: A condition in which blood acids are elevated
  • Neurogenic shock: Shock caused by a brain or spinal cord injury

Hypotensive Syndromes

Hypotensive syndrome is the term used when more than one factor causes a sudden drop in blood pressure. Usually a person has an underlying condition that is then triggered by doing something such as standing up after sitting or experiencing severe emotional distress.

Hypotensive syndromes tend to come on suddenly, sometimes with dramatic symptoms, including extreme dizziness and unconsciousness.

Some common hypotensive syndromes include:

  • Neurogenic orthostatic hypotension (NOH) is when a change in body position, such as rising from a chair or bed, causes a dramatic drop in blood pressure. NOH is caused by an underlying neurologic disorder that affects the autonomic nervous system, including neurodegenerative disorders like Parkinson's disease and Lewy body dementia as well as diabetic nerve damage.
  • Orthostatic hypotension (OH) has the same symptoms as NOH. It is brought on by non-neurologic causes such as decreased cardiac output and extreme vasodilation. Drugs such as diuretics, tricyclic antidepressants, and medications for high blood pressure can also cause OH.
  • Supine hypotensive syndrome occurs in later pregnancy when the weight of the baby presses down on two of the largest blood vessels in the body, called the aorta and the inferior vena cava. This decreases the flow of blood to the heart.
  • Postprandial hypotension occurs immediately after eating when blood is diverted to the intestines to aid with digestion. This temporarily robs the brain of blood and oxygen. It is most common in older adults and generally occurs within 30 to 75 minutes of eating.
  • Vasovagal syncope is an overreaction to certain emotional triggers, such as the sight of blood or extreme emotional distress. This leads to a steep drop in blood pressure and fainting (syncope). It is caused by the overactivation of the vagus nerve, which relays nerve signals from the heart, liver, lungs, and gut to the brain.
  • Situational reflex syncope also involves the vagus nerve, albeit directly. It occurs when physical pressure is placed on the nerve. Examples include straining during a bowel movement, lifting a heavy weight, or standing for too long in one place. Urinating after taking a vasodilating drug like Cialis (tadalafil) can also trigger reflex syncope.
  • Carotid artery syncope involves the compression of the internal carotid artery of the neck. Wearing a tight collar, shaving, or turning the head can cause a sudden drop in blood pressure, especially in older people or those with carotid artery stenosis.


A blood pressure cuff called a sphygmomanometer can tell you how low your blood pressure is, but it can't tell you what caused the sudden drop.

For this, the doctor will need to review your medical history, family history, current symptoms, and medications. Then they will perform some of the following tests to figure out the cause:

  • Valsalva maneuver: An in-office test used to diagnose orthostatic hypotension. You blow hard through pursed lips to see how it affects your blood pressure and heart rate.
  • Blood tests: These can help reveal underlying causes of acute hypotension, such as diabetes, anemia, hypoglycemia, thyroid problems, kidney problems, and hormonal imbalances.
  • Urinalysis: A urine test can help diagnose kidney disease.
  • Electrocardiogram (ECG): An ECG measures electrical activity in the heart to detect rhythm disorders, heart failure, and other cardiovascular problems.
  • Echocardiogram: This test uses sound waves to create video images of the heart to detect structural defects like heart valve leakage.
  • Imaging tests: Computed tomography (CT), magnetic resonance imaging (MRI), and X-rays are used to detect internal bleeding, structural heart problems, kidney problems, or a brain or spinal cord injury.
  • Tilt table testing: This measures heart function and blood pressure as the body is tilted at different angles on an adjustable table. It is mostly used to diagnose postural hypotension.
  • Cardiac stress testing: A stress test measures a person's heart function and blood pressure while they are running on a treadmill or pedaling a stationary bike. It is primarily used to diagnose coronary artery disease.

When to See a Healthcare Provider

Generally speaking, if you have recurrent symptoms of hypotension, even if symptoms are relatively mild (such as dizziness when rising from a chair), it is in your best interest to see a healthcare provider.

On the other hand, you need to call 911 or seek immediate emergency if you experience signs of shock. When this happens, your blood pressure has dropped so steeply that organs are deprived of adequate blood flow and oxygen, causing symptoms like:

  • Pale, cold, clammy skin
  • Shallow, rapid breathing
  • Difficulty breathing
  • Dizziness or lightheadedness
  • Nausea or vomiting
  • Anxiety
  • Confusion or disorientation
  • Rapid heartbeat
  • Heart palpitations (skipped heartbeats)
  • Dry mouth
  • Low urine output or dark urine
  • Fainting


Call 911 or go to your nearest emergency room if signs of shock develop. If left untreated, shock can lead to permanent organ damage, cardiac arrest, and even death.


The treatment of acute hypotension varies based on the underlying cause. If the condition is not a medical emergency, you should either sit or lie down immediately and raise your feet above heart level. If you are dehydrated, you should replenish lost fluids and seek immediate medical attention if the symptoms are severe.

If hypovolemic or hemorrhagic shock is involved, you may be given an intravenous (IV) saline solution or a blood transfusion. Septic shock may require IV antibiotics, while anaphylactic shock requires epinephrine (adrenaline).

If hypotension is related to extreme vasodilation or decreased cardiac output, medications such as vasodilators (like midodrine) or drugs to stimulate the heart (like digitalis) may be prescribed to improve heart function and output.

People with severe postural hypotension may benefit from the use of the anti-inflammatory steroid fludrocortisone.

Compression socks are often prescribed for people with orthostatic hypotension to prevent the pooling of blood in the legs. Wearing them keeps more blood in the upper body.


A sudden drop in blood pressure can occur for a variety of reasons. Some of these are not serious. In some cases, though, it may be a sign of something more serious, and even life-threatening. Serious underlying causes usually have other symptoms.

It is important not to ignore signs of hypotension. This is especially true if the drop is sudden and severe. Hypotension can often be treated successfully. The underlying cause, on the other hand, may require extensive treatment by a specialist, such as a cardiologist, neurologist, or endocrinologist.

14 Sources
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By Jeanette Bradley
Jeanette Bradley is a noted food allergy advocate and author of the cookbook, "Food Allergy Kitchen Wizardry: 125 Recipes for People with Allergies"