Causes and Risk Factors of Low Blood Pressure

In This Article

African American doctor checking senior man's blood pressure
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Many things can cause your blood pressure to be too low. It can be due to factors that are not part of an underlying disease, but instead can be due to dehydration or the side effects of a medicine. But it may be related to heart problems, hormone disturbances, neural conditions, or pregnancy.

Common Causes

The cause of low blood pressure varies by the type. The three main types are orthostatic hypotension, neurally mediated hypotension, and severe hypotension linked to shock.

Orthostatic Hypotension

One especially important cause of low blood pressure is orthostatic hypotension, which is sometimes referred to as postural hypotension. This phenomenon happens when blood pressure drops rapidly during changes in body position—usually when changing from sitting to standing. When this condition is present, it causes the classic signs that the blood pressure is too low, like dizziness, blurry vision, and fainting.

Normally, your nerve receptors signal when you are rising and your central nervous system responds by telling the muscles in the walls of your arteries to contract to increase your blood pressure, as well telling your heart to beat faster. This keeps the blood from pooling in the lower portion of your body. In orthostatic hypotension, this blood pooling results in less blood reaching your brain, lower blood pressure, and the woozy symptoms.

Orthostatic hypotension is seen in these conditions:

  • Pregnancy
  • Dehydration (which can be due to sweating, not drinking enough, vomiting, or diarrhea)
  • Older age (especially after a meal, when it is called postprandial hypotension)
  • Heart conditions
  • Anemia
  • Severe infections
  • Thyroid disorders
  • Low blood sugar and diabetes
  • Pulmonary embolism
  • Nervous system disorders including Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, Guillain-Barre syndrome, and neuropathy

Orthostatic hypotension may also be a side effect from certain medications, especially diuretics or other high blood pressure medications, like beta blockers. Medicines used to treat erectile dysfunction and certain psychiatric disorders can also cause low blood pressure.

You may also experience orthostatic hypotension simply by being out in the heat or being immobile for a long period.

Neurally Mediated Hypotension

Problems with the nervous system—especially disorders of the autonomic nervous system, including POTS and vasovagal syncope—can cause low blood pressure after extended periods of standing. Emotional stress can also be a trigger of neurally mediated hypotension.

In these conditions, there is poor communication between your brain and your heart, sending false signals that your blood pressure is high, so your heart slows and that drops your blood pressure further.

Autonomic neuropathy and peripheral neuropathy, which are characterized by nerve damage and can be caused by diseases like diabetes, also affect

Severe Hypotension Related to Shock

While some of the causes of severe hypotension in shock may also cause orthostatic hypotension, in shock the drop is much more severe and doesn't return to normal. The causes of hypotensive shock include:

  • Major blood loss (internal or external)
  • Septic shock from infection or toxins
  • Severe fluid loss from diarrhea, burns, or overuse of diuretics
  • Cardiogenic shock due heart attack, arrhythmia, or pulmonary embolism
  • Vasodilatory shock seen in head injury, liver failure, poisoning, or anaphylaxis.

Shock is a medical emergency and you must call 9-1-1 to get medical help.

Genetics

For the most part, having low blood pressure is a good thing. Unless it occurs suddenly or produces symptoms, there is usually nothing to worry about. In fact, when you have low blood pressure, you have a reduced risk of developing heart disease, having a heart attack or experiencing a stroke.

A study conducted by a team of researchers at Howard Hughes Medical Institute found that a small portion of the population have a gene mutation that not only gives them lower blood pressure but also lowers their risk of heart disease, kidney disease, and stroke. In fact, according to the researchers, people who carry the mutation have a 60 percent reduction in developing hypertension, or high blood pressure, by the time they are 60 years old.

A 2012 study looked at gene variants that were associated with blood pressure and did not find that they had much influence on whether or not a person had orthostatic hypotension. While orthostatic hypotension is seen more often in people who have close relative with the condition, it hasn't been linked to specific inheritance patterns.

Cardiovascular

Sometimes your blood pressure is impacted by the function or structure of your heart. This can lead to orthostatic hypotension or, in severe cases, to cardiogenic shock. Here are some common issues that impact your blood pressure:

  • Heart problems that cause low heart rate
  • Heart issues resulting in diminished heart strength
  • A decrease in the amount of blood supplied to the body

A healthy blood pressure is below 120/80 millimeters of mercury, or mmHg.

Too low blood pressure is defined as below 90/60 mmHg. At that pressure, your brain and other organs may not receive enough blood to function properly.

The buildup of plaque in your arteries that comes with aging narrows them and can reduce the blood flow to your heart and brain. This can contribute to hypotension.

Lifestyle Risk Factors

Blood pressure can impacted by other factors, including your diet, exercise, and age. Here is an overview of some additional risk factors for low blood pressure:

  • Deficiencies of essential nutrients, such as folic acid or iron, can cause the number of red blood cells or the concentration of hemoglobin to decrease, resulting in anemia.
  • Alterations in blood sugar, like those caused by diabetes, can lead to hypotension.
  • Some older patients, especially those with existing high blood pressure, can experience postprandial hypotension, where the blood pressure drops suddenly after eating a large meal.
  • Be sure to drink appropriate amounts of water and/or sports drink when exercising to prevent dehydration. For longer periods of exertion or when you are sweating more, you need to replenish salt (electrolytes) as well to maintain good blood pressure. This is provided in sports drinks.

A Word From Verywell

Feeling a little woozy when you stand up suddenly is something most people experience occasionally. But if it happens frequently, it may be a concern. If your low blood pressure is accompanied by symptoms such as dizziness, lightheadedness, fatigue, or fainting, you should talk with your doctor right away.

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