An Overview of Low Blood Pressure

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Given the well-known consequences of high blood pressure (hypertension), low blood pressure (hypotension) might seem like a good thing. While maintaining a healthy blood pressure (below 120/80 millimeters of mercury, or mmHG) can protect you from a host of health issues, too low blood pressure—defined as below 90/60 mmHg—can prevent your organs from getting adequate amounts of the oxygenated blood they need to function properly.

Hypotension is of particular concern for vital organs like the brain, especially when the drop in blood pressure occurs suddenly.

Blood Pressure Readings

The top number is the systolic blood pressure, which refers to the pressure created in the arteries with each heartbeat.

The bottom number is the diastolic blood pressure, or the pressure in the arteries when the heart is resting between each beat.

Symptoms

If you have low blood pressure but don’t experience any symptoms, then your blood pressure is most likely not a problem. However, if you do experience symptoms, you need to talk to your healthcare provider. Signs and symptoms of low blood pressure include:

  • Lightheadedness or dizziness
  • Fainting (syncope)
  • Blurred vision
  • Difficulty concentrating
  • Cool, clammy, pale skin
  • Shallow, rapid breathing
  • Thirst and dehydration
  • Fatigue
  • Nausea

Causes

The arteries have a muscular layer that respond to signals from nerve receptors throughout the body. These signals tell the arteries to expand or contract as needed to continue to deliver oxygen efficiently when and where you need it.

However, when the nervous system does not react quickly to compensate for the change in pressure, your blood may pool in the lower portions of the body. When this occurs, it can result in reduced blood flow to the brain, causing a feeling of dizziness or lightheadedness and a drop in your effective blood pressure.

There are many different reasons why you may be experiencing symptoms of low blood pressure. For instance, blood pressure can be impacted by not drinking enough water, getting up too quickly, taking certain medications as well as having certain conditions like hypoglycemia, heart arrhythmias, or hypothyroidism.

One common cause of low blood pressure is known as orthostatic or postural hypotension. Under normal circumstances, when you stand suddenly or rise up after lying down, the nerve receptors in your body send signals through the central nervous system to your arteries, causing the muscles in the artery wall to contract and increase the blood pressure enough to deliver more oxygen to supply your brain. Your central nervous system also signals your heart to beat more rapidly in order to compensate for the change in your posture.

But sometimes, your nervous system does not respond like it should and your blood remains pooled in the lower portion of your body. When this happens, you feel dizzy, lightheaded, and in some cases may faint.

Your blood pressure also drops. When this occurs, you are likely experiencing orthostatic or postural hypotension . Neurally mediated low blood pressure also can occur when you stand for a long period of time without changing position.

In addition to reduced response in the central nervous system, plaque may build up in your arteries with aging. When this happens, it creates narrowed arteries that may further reduce blood flow to your heart and brain. Autonomic neuropathy and peripheral neuropathy, which are characterized by nerve damage and can be caused by diseases like diabetes, also affect the body’s ability to regulate blood pressure, causing postural hypotension.

Other common causes of low blood pressure include:

  • Dehydration, which can result from vomiting, diarrhea, and excessive sweating
  • Hemorrhage, or blood loss, which can overwhelm the body's ability to compensate for reduced blood volume
  • Medications: In addition to high blood pressure medications, which can alter both arterial pressure and heart rate, nitrates used to treat chest pain, medications for erectile dysfunction, some antidepressants, and antipsychotic medications are known to cause low blood pressure. Medicines used to treat people with Parkinson’s disease are also associated with postural hypotension.
  • Hormonal problems, such as hypothyroidism or low blood sugar (hypoglycemia)
  • Heart failure, which results in ineffective pumping by the heart
  • Arrhythmias (irregular heart rhythms), which prevent the heart from generating adequate contractile strength
  • Liver disease
  • Pregnancy
  • Emotional stress: Blood pressure can drop suddenly and cause fainting or lightheadedness in response to significant emotional stress. In these cases, your central nervous system may be overwhelmed.
  • Sepsis, which is caused by an overwhelming infection and the body’s immune response to it
  • Anaphylaxis, which is a severe allergic reaction that causes a sudden and potentially fatal drop in blood pressure. Common causes of anaphylactic reactions include food allergies or allergies to medications like penicillin. Epinephrine is used to constrict the arteries and increase blood pressure in people who are having an anaphylactic reaction.

Diagnosis

Again, hypotension is defined as a blood pressure reading below 90/60 mmHg. When low blood pressure is detected, the doctor's goal is then to find the underlying cause.

During your exam, your physician will take your blood pressure and ask about your personal medical history, including any medications and supplements you are taking.

Your doctor also might recommend the following tests to further diagnose your condition.

  • Blood tests to identify conditions that may be impacting your blood pressure, like diabetes or anemia
  • Electrocardiogram (ECG), which can indicate issue with your heart's rhythm and structural abnormalities
  • Echocardiogram, which produces detailed images of your heart's function and structure
  • Stress test to monitor your heart rate and blood pressure while walking on a treadmill
  • Tilt table test to determine if your blood pressure is impacted by standing from a prone position

Treatment

Because low blood pressure can be the result of many different conditions, treatment may be specific to the condition causing it. Here are some of the most common causes of low blood pressure with associated treatments.

  • Decreased Blood Volume: This can occur as a result of dehydration, or from blood loss due to trauma or internal bleeding. It is treated by volume replacement with fluids and sometimes with blood products.
  • Orthostatic or postural hypotension as a result of central nervous system conditions is more common as we age. This issue may require further testing, until the cause of your postural hypotension is identified. Until then, avoid things that provoke the problem, such as getting up suddenly from a seated or reclining position.
  • Medications that can result in hypotension include beta-blockers, calcium channel blockers, ACE inhibitors, and diuretics, which are all used to treat hypertension. Other drugs, including antidepressants, antipsychotics, and drugs for treatment of Parkinson’s disease, may be the cause. If you have recently started a new medication and have low blood pressure, your healthcare provider may reduce your dose, substitute another drug, or discontinue treatment.
  • Hormonal (endocrine) causes of low blood pressure include adrenal insufficiency, known as Addison’s disease, low thyroid activity (hypothyroidism), a disease of the parathyroid glands, and low blood sugar. When your endocrine system is the cause of hypotension, replacement of the missing hormone may be required. If your endocrine problem is the result of a tumor, there are a variety of options, depending upon the location and type of tumor.
  • Pregnancy also can cause low blood pressure. Blood pressure changes during pregnancy in a predictable way, depending upon how quickly the body's blood volume adapts to the needs of the fetus. However, when the uterus puts pressure on the major blood vessels this can cause low blood pressure. When it does, a change in position is needed. Towards the end of pregnancy, it is helpful to recline on the left side, which reduces pressure on the blood vessels from the growing uterus and fetus.
  • Nutritional deficiencies, including iron deficiency, vitamin B12, and folate, can cause anemia, which can lead to low blood pressure. Replacement therapy will be helpful, but some people will need fluids or even a blood transfusion.
  • Neurally-mediated low blood pressure refers to low blood pressure after standing for a long period of time or low blood pressure with syncope resulting from a sudden dramatic emotional event. Younger individuals are most often affected and the condition usually resolves quickly.
  • Anaphylaxis is a severe allergic reaction that can be fatal. It can cause extremely low blood pressure, breathing problems, swelling in the throat, and hives. Common causes include penicillin allergy, food allergies, and bee stings. Individuals who know they have a severe allergy should not only avoid allergens, but they also should carry an EpiPen, which is a self-injector of the medication epinephrine. Epinephrine is also used to treat anaphylaxis in the emergency department.
  • Changes in your heart rhythm can result in low blood pressure and syncope. If this is the case, you may need an anti-arrhythmic medication or a pacemaker. To establish this diagnosis, your physician may order a 24-hour monitor for you, which you will wear in your home as you go through your daily activities.
  • Heart failure can cause low blood pressure in very severe cases. Heart failure is a progressive disease best managed by a cardiologist. There are medications that can increase the heart's pumping action, but some people may need a heart transplant.
  • Liver disease, including cirrhosis, can cause low blood pressure because the liver is not able to produce the proteins needed to keep fluid within the blood vessels. Cirrhosis is best managed by a gastroenterologist or hepatologist, who can prescribe medications to reduce the symptoms. Because cirrhosis is the end stage of liver disease, some individuals may require a liver transplant.
  • Septic shock is the result of an overwhelming infection and the body’s immune response. It can be caused by bacterial toxins in the bloodstream. In these cases, it is important to treat the infection, but supportive care—including intravenous (IV) fluid and medications to raise your blood pressure (vasopressors)—is sometimes required until you are on the way to recovery.

Staying hydrated, exercising regularly, eating well, and reducing stress all help keep blood pressure levels in the healthy range.

A Word From Verywell

Generally, low blood pressure is most significant when it occurs suddenly or when it is the result of another disease. If you are experiencing any symptoms of hypotension, do not delay in speaking with your healthcare provider.

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Article Sources

  • Anaphylaxis. (n.d.). Retrieved from http://www.aaaai.org/conditions-and-treatments/allergies/anaphylaxis.aspx
  • Freeman R. Clinical practice. Neurogenic orthostatic hypotension. N Engl J Med. 2008 Feb 7. 358(6):615-24. [Medline].
  • Mathias CJ. Disorders of the autonomic nervous system. Neurology in Clinical Practice. Boston, Mass: Butterworth-Heinemann; 1996. 1953-81.
  • Mukai S, Lipsitz LA. Orthostatic hypotension. Clin. Geriatr. Med. 18(2), 253–268 (2002).
  • Oner T, Guven B, Tavli V, Mese T, Yilmazer MM, Demirpence S. Postural Orthostatic Tachycardia Syndrome (POTS) and Vitamin B12 Deficiency in Adolescents. Pediatrics. 2014 Jan. 133(1):e138-42.