What happens when your blood pressure is too low

You’ve probably heard of hypertension—when blood pressure is too high. But what happens when you have the opposite problem?

By Todd Hartley | Jun. 29, 2021 Medically reviewed by Lindsey Hudson, APRN, NP-C, CDCES

Most people know that when your blood pressure is too high—a condition called hypertension—it can contribute to heart attacks, heart disease, and other health concerns. But what about hypertension’s opposite, hypotension? What happens when your blood pressure is too low? If high blood pressure is bad, is lower blood pressure always good, or are there any health concerns people with hypotension should look out for?

“The main issue with low blood pressure is if patients are experiencing symptoms of dizziness, lightheadedness, or the sensation that they’re going to lose consciousness,” says Eugene Yang, MD, a professor of medicine at the University of Washington and chair of the American College of Cardiology’s Prevention Section and Leadership Council. “That’s what we worry about because, obviously, losing consciousness or passing out can be dangerous. If somebody’s driving a car or doing something that could put them in danger, they can cause significant trauma to themselves.”

Older adults, who are most at risk of suffering trauma in a fall, are more likely to experience symptoms of low blood pressure. They’re also more likely to develop low blood pressure as a result of medicines they may be taking to treat high blood pressure.

What is low blood pressure?

A blood pressure reading consists of two numbers, for example: 120 over 80. The first number is your systolic pressure, the force your heart exerts on the walls of your arteries each time it beats. The second number is diastolic pressure, the force your heart exerts on the walls of your arteries in between beats. Both systolic pressure and diastolic pressure are measured in millimeters of mercury (mmHg).

According to the American Heart Association, there is no particular number at which day-to-day blood pressure is considered too low, as long as you have no symptoms. The National Heart, Lung, and Blood Institute, on the other hand, describes hypotension as blood pressure that is lower than 90/60 mmHg. “In general, a systolic blood pressure that’s between 110 and 140 is the range that seems to be associated with optimal cardiovascular health,” says Dr. Yang.

“Blood pressure can vary quite a bit in an individual throughout the day, and there is quite a range of blood pressure in healthy populations,” adds Donna K. Arnett, Ph.D., dean of the University of Kentucky College of Public Health and professor of epidemiology.

If your systolic blood pressure is well below 110 at every reading, your healthcare provider may want to keep an eye on it, but if you have no symptoms, a low number is nothing to be alarmed about. However, if your blood pressure drops suddenly from, say, 120 to 90 or less, it could be the result of an underlying cause, and you should talk to a healthcare provider.

Low blood pressure symptoms

For most people, long-term low blood pressure is not an issue and often goes unnoticed. More serious cases of hypotension may produce the following symptoms:

Dizziness or lightheadedness
Fainting (also called syncope)
Heart palpitations
Blurred vision
Fatigue
Depression
Lack of concentration
Nausea
Dehydration and thirst
Cold, clammy, pale skin
Rapid breathing

In rare cases of extreme hypotension, when the body’s vital organs fail to get the oxygen and nutrients they need, low blood pressure can lead to shock, a life-threatening condition that requires immediate medical attention. Other signs of shock include sweaty skin, rapid breathing, a blue skin tone, or a weak and rapid pulse.

What causes low blood pressure?

Low blood pressure isn’t always linked to a medical condition. Prolonged bed rest and pregnancy (hypotension is common in the first 24 weeks) are possible causes of low blood pressure, and even standing too long can bring on a condition called neurally mediated hypotension, which can lead to dizziness, nausea, and fainting.

Low blood pressure often coexists with depression, but doctors aren’t sure about the relationship between the two. “This remains unclear,” says Arnett. “There is some evidence that an association exists between low blood pressure and depression that appears late in life (late-life depression, or LLD), but whether low blood pressure causes depression or depression causes low blood pressure is unknown at this time.”

Underlying medical conditions that can cause hypotension include:

Dehydration
Blood loss from an accident
Severe infection (septic shock or septicemia)
Allergic reaction (anaphylaxis or anaphylactic shock)
Heart problems, such as a low heart rate (bradycardia) or heart failure
Endocrine problems like hypothyroidism, parathyroid disease, adrenal insufficiency (Addison’s disease), low blood sugar, and, in some cases, diabetes
Anemia (this is often due to nutritional deficiencies like a lack of vitamin B-12 or folic acid)
Autonomic nervous system conditions such as Parkinson’s disease

Medications that can cause low blood pressure as a side effect include:

Diuretics (water pills), such as Lasix (furosemide) and Microzide (hydrochlorothiazide)
Alpha blockers, such as Minipress (prazosin)
Beta blockers, such as Tenormin (atenolol) and Inderal (propranolol)
Tricyclic antidepressants, such as Silenor (doxepin) and Tofranil (imipramine)
Erectile dysfunction drugs, such as Viagra (sildenafil) and Cialis (tadalafil), particularly when taken along with Nitrostat (nitroglycerin)
Drugs to treat Parkinson’s disease, such as Mirapex (pramipexole) and drugs containing Rytary (levodopa)

Diagnosis and types of hypotension

Once a healthcare provider has determined through a blood pressure reading that you have hypotension, diagnosis will focus on figuring out what is causing your blood pressure to be too low. Your healthcare provider will examine your medical history to look for underlying causes and may order a blood test to see if you have low blood sugar (hypoglycemia), high blood sugar (hyperglycemia), or a low red blood cell count (anemia).

To see if your heart is functioning the way it’s supposed to, the healthcare provider may order an electrocardiogram (ECG), which records your heart’s electrical signals and can detect irregularities in your heart rhythm, structural problems in your heart, and issues with the supply of blood and oxygen to the heart muscle.

If you are experiencing dizziness or neurally mediated hypotension, a tilt-table test may be performed. In this test, a person lies on a table that is tilted to raise or lower their upper body in order to evaluate how their body reacts to changes in position.

There are five main types of hypotension.

Orthostatic hypotension, or postural hypotension

This is a sudden drop in blood pressure when you get up from a seated or lying position. Orthostatic hypotension can cause chest, neck, or shoulder pain in addition to the other symptoms of low blood pressure. This condition is more common first thing in the morning and in older adults.

Neurally mediated hypotension

Brought on by standing for a long period of time, this condition occurs because of a miscommunication between the brain and the heart. Neurally mediated hypotension is more common in children and young people.

Postprandial hypotension

This is a drop in blood pressure that typically occurs one to two hours after eating a meal. Postprandial hypotension can cause people to feel lightheaded or dizzy and is most common in adults, people with high blood pressure, and people with autonomic nervous system disorders.

Severe hypotension linked to shock

The Cleveland Clinic calls shock the most extreme form of hypotension. When someone goes into shock, their blood pressure drops to dangerously low levels, and their organs and brain can’t get enough blood and oxygen to function correctly.

Multiple system atrophy with orthostatic hypotension

This is a rare disorder, also known as Shy-Drager syndrome; it is similar to Parkinson’s disease. Multiple system atrophy causes progressive damage to the autonomic nervous system, which controls involuntary bodily functions like blood pressure, heart rate, breathing, and digestion.

When is low blood pressure an emergency?

In most cases, low blood pressure is nothing to worry about unless you start to show symptoms of hypotension. If you notice mild symptoms, such as temporary dizziness or occasional blurred vision, make an appointment with a healthcare provider to have the condition checked out.

“If you’re having minor symptoms, like some lightheadedness or fatigue, and you have low blood pressure, that’s when you should contact your doctor and get evaluated to find out what’s causing it,” says Yang.

In rare cases, a sudden drop in blood pressure can lead to more serious complications like shock, heart attack, and even death. These situations require immediate medical attention. If you can, have someone get you to a hospital emergency room immediately. If you’re alone, call 911, and don’t try to drive yourself to a hospital.

“If someone has low blood pressure, call 911 if their heart rate increases, their breathing is shallow, they’re confused, or the person is cold and clammy,” says Arnett. “This is most likely shock and not just low blood pressure.”

What to do if blood pressure is too low

Most cases of low blood pressure that don’t cause symptoms—or only cause mild symptoms—don’t require treatment. When treatment is necessary, it generally depends on the underlying condition causing your blood pressure to be too low. Hypotension caused by medications is usually treated by stopping use of the medication or changing the dosage. Low blood pressure due to dehydration can be treated by making sure to drink more fluids. Hypotension resulting from blood loss is treated by stopping the bleeding and administering intravenous fluids or a blood transfusion.

To help prevent orthostatic hypotension at home, be aware of how you stand up, get up in the morning, or change positions. Other home-care remedies that can help treat low blood pressure include:

1. Salt

“Sodium intake has a large influence on blood pressure in some individuals, and an increase in salt intake may help,” says Arnett. “But before increasing salt intake, it is very important to know the cause of the low blood pressure. If the cause is cardiac in nature, you should consult with your physician about sodium intake.”

RELATED: Is salt bad for you?

2. Diet

Eating smaller, healthier meals and limiting carbohydrates can help keep your blood pressure stable—so can limiting or avoiding alcohol.

3. Water

Fluids will help increase blood volume and prevent dehydration, which can help prevent low blood pressure.

4. Exercise

Doing exercises that raise your heart rate for 30-60 minutes a day helps increase your overall heart health.

5. Compression stockings

Tight elastic stockings can help decrease the pooling of blood in your legs and can help if you have to stand for long periods of time.

6. Medications

“If behavioral things like wearing compression stockings, increasing fluid intake, and minimizing alcohol don’t work, then there are what we call volume expanders, or medications that increase your intravascular blood volume,” says Yang.

Medications that healthcare providers may prescribe for hypotension—particularly orthostatic hypotension—include: