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Low Blood Pressure (Hypotension)


Disease: Low Blood Pressure (Hypotension) Low Blood Pressure (Hypotension)
Category: Cardiovascular diseases
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Disease Definition:

For many people, low blood pressure could cause symptoms of dizziness and fainting or mean that they have serious heart, endocrine or neurological disorders, despite the fact that low blood pressure may seem to be something to strive for. The brain and other vital organs could be deprived of oxygen and nutrients due to a severely low blood pressure, which could cause shock, a life-threatening condition.

Despite the fact that blood pressure could vary from one person to another, however, it will be considered low blood pressure in case the blood pressure reading is 90 millimeters of mercury (mm Hg) or less systolic blood pressure, which is the top number in a blood pressure reading, or 60 mm Hg or less diastolic blood pressure, which is the bottom number in a blood pressure reading.

The causes of low blood pressure could range from dehydration to problems with the way the brain signals the heart to pump blood. Low blood pressure is a treatable condition, but in order to be treated well, it's important to find out what is causing it.

Work Group:

Prepared by: Scientific Section

Symptoms, Causes


In some cases, an underlying problem could cause low blood pressure, particularly if it drops all of a sudden or is accompanied by signs and symptoms, such as:


  • Lack of concentration
  • Nausea
  • Lightheadedness or dizziness
  • Cold, clammy, pale skin
  • Syncope (Fainting)
  • Depression
  • Blurred vision
  • Thirst
  • Fatigue
  • Rapid and shallow breathing

A low blood pressure isn't serious in many cases. A person is likely to be monitored during routine exams in case they have consistently low readings but feel fine. Occasionally, dizziness or lightheadedness could be a relatively minor problem, which could occur due to too much time in the sun or a hot tub. In these situations, it's more important how quickly the blood pressure drops rather than how far.

Still, it's important to see a doctor if the patient experiences any signs or symptoms of hypotension because they sometimes can point to more serious problems. It can be quite helpful to keep a record of these symptoms, when they occur and what someone was doing at the time.



Endocrine problems:
Low blood pressure could be caused by hypothyroidism or hyperthyroidism. Low blood pressure could also be triggered by Addison's disease (adrenal insufficiency), hypoglycemia and in some cases, diabetes.

Heart problems:
Extremely low heart rate (bradycardia), heart failure, heart valve problems and heart attack are some of the heart conditions that could lead to low blood pressure. Because these conditions prevent the body from being able to circulate enough blood, they end up causing low blood pressure.

Blood pressure is likely to drop because a woman's circulatory system expands rapidly during pregnancy. Usually, the systolic pressure drops by 5 to 10 points, and diastolic pressure drops by 10 to 15 points during the first 24 weeks of pregnancy. This is quite normal, and after the woman has given birth, her blood pressure will return to the pre-pregnancy level.

Severe infection (septicemia):
When an infection in the body enters the bloodstream, septicemia could occur. These conditions could lead to septic shock, which is a life-threatening drop in blood pressure.

In case someone becomes dehydrated, their body will lose more water than it will take in. Weakness, dizziness and fatigue could be caused by even mild dehydration. Dehydration could be caused by the overuse of diuretics, fever, strenuous exercise, vomiting and severe diarrhea.
A hypovolemic shock, which is a life-threatening complication of dehydration, is far more serious. When low blood volume causes a sudden drop in blood pressure and a reduction in the amount of oxygen reaching the tissues, the hypovolemic shock occurs. A severe hypovolemic shock could cause death within a few minutes to hours in case it's left untreated.

Anaphylaxis is a severe and potentially life-threatening allergic reaction, which could cause a drop in blood pressure, itching, hives, a swollen throat and breathing problems. Latex, certain medications, foods and insect venoms are some of the common triggers of anaphylaxis.

Blood loss:
A severe drop in blood pressure could be caused by losing a lot of blood from a major injury or internal bleeding, which reduces the amount of blood in the body.

Lack of nutrients in the diet:
Low blood pressure could be due to anemia, which is caused by the lack of the vitamins B-12 and folate. Anemia is a condition in which the body doesn't produce enough red blood cells.



  • Certain types of antidepressants, such as tricyclic antidepressants
  • Diuretics
  • Beta blockers
  • Alpha blockers
  • Sildenafil, especially in combination with nitroglycerine, which is another heart medication
  • Drugs for Parkinson's disease

Depending on the cause and other factors, low blood pressure is usually put into different categories. Some of the types of low blood pressure are:

Postprandial hypotension:
The sudden drop in blood pressure after eating is called postprandial hypotension. Usually, older adults are affected by this type. A large amount of blood flows to the digestive tract after someone eats, just as gravity pulls blood to the feet when someone stands. Usually, by increasing the heart rate and constricting certain blood vessels to help maintain normal blood pressure, the body counteracts this process. However, these mechanisms fail in some people, causing falls, dizziness and faintness. People with high blood pressure or autonomic nervous system disorders such as Parkinson's disease are usually affected by postprandial hypotension. These symptoms could be reduced by lowering the dose of blood pressure drugs and eating small, low-carbohydrate meals.

Postural or orthostatic hypotension:
In this type, when someone stands up from a sitting position or if they stand up after lying down, their blood pressure will suddenly drop. Normally, whenever someone stands, gravity causes blood to pool in the legs. By increasing the heart rate and constricting blood vessels, the body will compensate for this, and thus, ensure that enough blood returns to the brain. However, in people with postural hypotension, dizziness, lightheadedness, blurred vision and even fainting could result because this compensating mechanism will fail and blood pressure will fall.

Some of the conditions that could cause postural hypotension may include:


  • Heart problems
  • Large varicose veins
  • Diabetes
  • Prolonged bed rest
  • Certain neurological disorders
  • Pregnancy
  • Excessive heat
  • Burns
  • Dehydration

Medications used to treat high blood pressure, such as calcium channel blockers, beta blockers, diuretics and ACE (angiotensin- converting enzyme) inhibitors; medications used to treat erectile dysfunction and Parkinson's disease; and antidepressants are some of the medications that could cause postural hypotension.

About 20% of people over 65 experience postural hypotension, which means that it's quite common in older adults. However, otherwise healthy young people who stand up suddenly after sitting with their legs crossed for long periods or after working for a time in a squatting position could also be affected by postural hypotension. In young people, postural hypotension is usually harmless.

Multiple system atrophy with orthostatic hypotension:
This form is also called Shy-Drager syndrome. It is a rare disorder that causes progressive damage to the autonomic nervous system that controls involuntary functions, such as heart rate, digestion, blood pressure and breathing. The main characteristic of this condition is severe orthostatic hypotension in combination with very high blood pressure when lying down; however, it is also associated with incontinence, muscle tremors, problems with coordination and speech and slowed movement. Within 7 to 10 years of diagnosis, this condition proves fatal, and it has no cure.

Neurally mediated hypotension:
After standing for long periods, this disorder causes blood pressure to drop. Fainting, dizziness and nausea are some of its symptoms.

Young people are mostly affected by neurally mediated hypotension and it occurs due to a miscommunication between the heart and the brain. Someone’s blood pressure will fall when they stand for extended periods as blood pools in their legs. The body would normally make adjustments to normalize the blood pressure. However, if someone has neurally mediated hypotension, the nerves in the heart's left ventricle will signal the brain that blood pressure is too high instead of too low, and so the blood pressure will decrease even further because the brain will lessen the heart rate. This will end up causing lightheadedness and fainting because more blood will pool in the legs and less blood will reach the brain.



Not only weakness and dizziness, but also fainting and a risk of injury from falls could be caused by even the moderate forms of low blood pressure. Damage to the heart and brain could be caused by severely low blood pressure, which could deprive the body of enough oxygen to carry out its normal functions.


If a low blood pressure doesn't cause any signs or symptoms, or causes only mild symptoms such as brief episodes of dizziness when standing, it requires treatment only in some rare cases.
Treatment will depend on the underlying cause if someone experiences symptoms, and usually, instead of treating the low blood pressure itself, doctors try to treat the primary health problem, such as diabetes, dehydration, hypothyroidism or heart failure. However, if the low blood pressure is caused by medications, changing the dose of the medication or stopping it may treat the condition.

Raising the blood pressure and reducing the signs and symptoms will be the goal of treatment in case what exactly is causing the low blood pressure is not clear or treatment isn't effective. This could be done in several ways depending on the patient’s health status, age, and the type of low blood pressure they have:

Using more salt:
Because sodium could raise blood pressure, in some cases dramatically, people will probably be recommended limiting the amount of salt in their diet. This could be a good thing for people with low blood pressure. However, it's quite important to check with the doctor before increasing the salt in the diet because excess sodium could lead to heart failure, particularly in older adults.

Drinking more water:
If someone has low blood pressure, drinking more water will be especially beneficial for them, even though nearly everyone can benefit from drinking enough water. Fluids help prevent dehydration and increase blood volume; in treating hypotension, these two things are quite important.

Wearing compression stockings:
Pooling of blood in the legs could be reduced by the same elastic stockings that are commonly used to relieve the pain and swelling of varicose veins.

Orthostatic hypotension, which is the low blood pressure when standing up, could be treated by several medications, either used alone or together. Fludrocortisone is a drug that helps boost blood volume, which raises blood pressure. This drug is usually used to treat orthostatic hypotension. To raise standing blood pressure levels in people with chronic orthostatic hypotension, doctors usually use midodrine, which restricts the ability of the blood vessels to expand, raising blood pressure.


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