Hypotension is the medical term for low blood pressure, which is defined as below 90/60. This occurs when the pressure on the blood vessel walls falls below normal limits. Low blood pressure that does not cause symptoms is generally considered to be a sign of good cardiovascular health because there is less stress on the heart and blood vessels.

However, there are a number of forms of low blood pressure that require diagnosis, evaluation and treatment. People may seek treatment for low blood pressure if they experience symptoms such as dizziness or syncope (fainting) from lack of oxygen to the brain. Low blood pressure may be due to medications (e.g., blood pressure medications) or other causes, and changing medications or other treatments may be necessary.

Hypotension is the medical term for low blood pressure, which is considered to be under 90/60. Usually, borderline-low or slightly low blood pressure readings produce no symptoms and may require no treatment. Low blood pressure can be a sign of good health in some people with no symptoms (e.g., athletes). It indicates that the hearts, lungs and blood vessels are well conditioned and in good working order. However, it may also be an indication that the body is unable to properly regulate blood pressure. In these cases, low blood pressure may require treatment.

There are a number of forms of low blood pressure that require medical diagnosis and treatment. The two most common are orthostatic hypotension and neurally mediated hypotension (NMH).

Orthostatic hypotension
Also called postural hypotension, orthostatic hypotension is a condition that is more likely to develop in people as they age. Therefore, it is often found in elderly patients. It may complicate the treatment of essential or isolated systolic hypertension (high blood pressure) because many patients with orthostatic hypotension also suffer from systolic hypertension when seated. Orthostatic hypotension is characterized by the body's inability to quickly regulate blood pressure after changes in position. People who have this condition may feel temporarily light-headed after standing up or rising from a lying position. People who suffer from this condition are counseled to change position gradually: sit before standing, and stand before walking. The patient's medication will usually be re-evaluated or altered depending on their symptoms.

A related form of hypotension is known as postprandial hypotension. This form of hypotension occurs between 15 and 90 minutes after people eat. It is more common among elderly patients.

Patients with orthostatic hypotension should avoid going for long periods without food or drink, and to avoid spending too much time in the sun. Fatigue, alcohol and heavy meals add to the likelihood and severity of these symptoms. Support stockings, increased salt intake, increased fluid intake and certain medications may help to alleviate the symptoms.

Neurally mediated hypotension (NMH)
Also known as neurogenic orthostatic hypotension, neurally mediated hypotension (NMH) is a condition in which the body does not regulate blood pressure well, especially when the person is upright. The condition often develops in young patients without heart disease who have hypotensive symptoms. It is thought to be a result of a communication problem between the brain and the nerve sensors that control blood pressure and heart rate.

In some cases, NMH is temporary and not serious. For example, a person may faint (vasovagal syncope) in certain situations such as after seeing blood, hearing bad news or getting an injection. Individuals may become pale and clammy, nauseous or develop an uncomfortable feeling in their stomach.

In other cases, NMH is more serious than orthostatic hypertension. People may have great difficulty or even an inability to stand for long periods of time. Other symptoms include dizziness, weakness, sweating, blurring of vision and near-fainting. Diagnosis hinges on ruling out other conditions, certain diagnostic tests (e.g.  electrocardiogram, tilt table test).

When blood pressure remains very low, or when there is a sudden, rapid drop in blood pressure, an individual's performance and health may be significantly impaired. While some patients with high blood pressure may have no symptoms, low blood pressure symptoms may prompt a patient to seek immediate medical attention. These symptoms may include:

If blood pressure becomes severely low, there is a danger that the body will not receive enough oxygen to carry out normal functions. Oxygen deprivation can result in impaired brain and heart functions, and difficulty breathing. With significantly low blood pressure, an individual can lose consciousness or go into shock.

The causes of low blood pressure (hypotension) are not always clear. It may be associated with one or more of the following:

People may also experience sudden and life-threatening drops in blood pressure (shock). Shock with a corresponding drop in blood oxygen supply will compromise normal body functions such as breathing, circulation, brain function and movement. Rapid drops in blood pressure that could be life-threatening can result from:

• Loss of blood or blood volume (e.g., due to hemorrhage or internal bleeding)
  
  
• Low body temperature (hypothermia)
  
  
• High body temperature (hyperthermia), perhaps due to unusually hot weather
  
  
• Severe allergic reaction to an injected substance (e.g., a bee sting)
  
  
• Reaction to a medication, under certain circumstances
  
  
• heart disease, or cardiac events such as acute myocardial infarction (heart attack) 
  
  
• Endocrine disorders
  
  
• Severe dehydration
  
  
• Severe blood infection (sepsis)

Individuals may also experience sudden drops in blood pressure that are not life-threatening. These drops may be due to the following:

• A particularly heavy menstrual period
  
• Unusually hot weather
  
• Mild to moderate dehydration
  
• Too much time in the sun, in a hot tub or in a sauna
  
• Sudden emotional shock

A physician always tries to determine the cause of low blood pressure (hypotension) to determine the treatment and to ensure that it is not due to a more serious problem, such as heart disease. Underlying heart disease, such as an abnormal heart rhythm (arrhythmia) or narrowing (stenosis) of a heart valve, can be life-threatening.

Important factors considered when making a diagnosis include the patient’s age, the conditions under which the symptoms occurred and the symptoms themselves. An electrocardiogram (EKG) and an echocardiogram are noninvasive tests that are essential. Blood tests (e.g., glucose test, complete blood count and hematocrit calculation) can help rule out hypoglycemia and anemia.

A 24-hour Holter monitor or a 30-day loop recorder may be necessary to record the heart’s electrical activity for a longer period of time. These devices are used while patients go about their daily routine to detect an abnormal heart rhythm or heart block. An exercise stress test or an electrophysiology study may also be helpful.

Serious forms of neurally mediated hypotension may also require a tilt test table. This test is often used to diagnose significant hypotension-related problems and to evaluate the body's reaction to its position and position changes over time. In a tilt table test, the patient lies down on a table and is strapped to it. The table is raised to an upright position where the patient may remain for up to one hour. blood pressure, heart rate and symptoms (e.g., dizziness or faintness) will be recorded. Results will help to determine diagnosis and any further treatment. Medications may be given to the patient during the study to enhance the sensitivity of the study and to guide treatment.

Treatment depends almost entirely on the presence of symptoms and the underlying cause(s) of low blood pressure. In some cases, a physician may prescribe medication either to raise the blood pressure or to prevent the heart from slowing down. Sometimes, an increase in salt intake may be prescribed as well as avoiding dehydration. For patients with postprandial hypotension, avoiding large meals and large amounts of carbohydrates may help regulate their blood pressure. Patients may also be advised to avoid alcohol and standing suddenly, especially after eating. 

Medications that raise blood pressure by increasing sodium retention and absorption may be prescribed. Individuals with orthostatic hypotension may be prescribed fludrocortison, a medication that increases blood volume and is typically well-tolerated by patients. Other drugs that may be prescribed include ephedrine, midodrine, nonsteroidal anti-inflammatory drugs (NSAIDs) and caffeine. Patients with neurally mediated hypotension may be prescribed beta blockers. In addition, compression leg stockings may be used to improve blood return to the heart.

Sometimes treatment is not necessary because the kidneys can naturally balance low blood pressure by retaining salt and water, thereby increasing blood volume to allow the heart to work more effectively.

However, this self-regulating system is not foolproof – increasing the retention of salt and water may ultimately end up worsening the condition. People are encouraged to speak to their physicians if they have had low blood pressure readings or related symptoms.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor or healthcare professional the following questions related to low blood pressure:

1. How can low blood pressure affect my health?
   
   
2. What is my blood pressure reading?
   
   
3. What level of blood pressure is too low for someone in my condition?
   
   
4. What type of hypotension do I have?
   
   

5. What do you suspect is causing my low blood pressure?
   

6. Will I need to undergo any tests for this condition?
   
   

7. What are my treatment options?
   
   

8. What are the benefits and risks of these treatments?
   
   
9. If I need medications, what will you prescribe?
   
   
10. How quickly will I see improvement with my condition?
    
    
11. How long will I need to stay on these medications?
    
    
12. What other lifestyle changes should I consider for my condition?
    
    
13. What symptoms indicate the need for immediate medical attention?
    
    
14. How can low blood pressure affect a pregnancy?