In medicine, low blood pressure (hypotension) refers to an abnormally low blood pressure. This is best understood as a physiologic state, rather than a disease. It is often associated with shock, though not necessarily indicative of it. Hypotension is not hypertension, which is high blood pressure, the opposite of hypotension. Hypotension is a fairly rare problem, hypertension is a much more common problem. Hypotension is usually not a serious problem, although in some cases it can be life threatening.

Blood pressure varies between individuals and throughout the day. Blood pressure is normally above 90/60 mmHg. Your blood pressure varies by large amounts, depending on what you are doing. The lowest blood pressures occur when you are asleep or if you relax all your muscles. Standing up, exercising or anxiety all cause an increase in blood pressure. In a single day your blood pressure may vary by 30 to 40 mmHg systolic with similar proportionate changes in diastolic pressure.

Hypotension usually means blood pressure that is lower than 90/60 mmHg (millimeters of mercury) or is low enough to cause symptoms. When the blood pressure is too low there is inadequate blood flow to the brain and other vital organs, light-headedness or fainting may occur.


Symptoms of low blood pressure (hypotension)

Cardinal symptom of hypotension is lightheadedness or dizziness. If the blood pressure is sufficiently low, fainting and often seizures will occur.

Hypotension, depending on one's own body chemistry and genetics, may often cause mild depression, mostly in regard to taking other medications which do not fit one's personal unique needs.

Low blood pressure is also associated with:

- Shortness of breath
- Irregular heartbeat (palpitations)
- Nausea
- Confusion
- Blurred vision
- General weakness
- Temporary loss of consciousness
- Profound fatigue


Types of Hypotension

Postural, or orthostatic hypotension

You may feel dizzy, or faint, after changing posture - for example, when you sit up from a lying position, or stand up from a sitting position. However, the fall in blood pressure usually only lasts for a few minutes as it adjusts to your new posture. This is known as postural, or orthostatic hypotension, and can affect you more as you get older. Similar symptoms may also occur after exercise.

Postprandial hypotension

Dizziness, light-headedness, faintness, and falls, are symptoms that can sometimes occur after eating, as a result of low blood pressure. This condition, known as postprandial hypotension, tends to occur more often in older people, particularly in those who have high blood pressure, or a condition such as Parkinsons disease, or diabetes.

After a meal, the intestines need a large amount of blood for digestion, and so the heart rate increases, and the blood vessels in other parts of the body constrict (narrow) to help maintain blood pressure. However, the heart rate of some elderly people may not increase enough, and their blood vessels may not constrict enough to maintain blood pressure. As a result, their blood pressure falls. Lying down after eating, and eating frequent, small, low-carbohydrate meals may help to reduce the effects of postprandial hypotension.

Neurally Mediated Hypotension

In this form of hypotension, blood pressure drops after a person has been standing for a long time. A person may feel dizzy, faint, or sick to the stomach as a result. NMH also can happen when a person faces an unpleasant, upsetting, or frightening situation.

NMH affects children and young adults more often than other age groups. Children often outgrow this form of hypotension.

Severe Hypotension Associated With Shock

Many times people will say a person has “gone into shock” as a result of an emotionally upsetting experience. But to doctors, the word “shock” has a different meaning. Shock is a life-threatening condition in which blood pressure drops so low that the brain, kidneys, and other vital organs can’t get enough blood to work properly. It is different from the other forms of hypotension because blood pressure drops much lower, and it is life threatening if not treated immediately. There are many causes of shock, including major loss of blood, certain severe types of infection, severe burns, severe allergic reactions, and poisoning.


Causes of hypotension>

- Drugs. Certain drugs can cause low blood pressure such as diuretics, anaesthetic, calcium blockers, some antidepressants and drugs given for hypertension (high blood pressure)

- Dehydration through loss of fluids (severe vomiting or diarrhoea, blood loss) and poor fluid intake

- Shock due to internal bleeding, severe infection and heart conditions leading to heart failure, such as a heart attack or viral infection of the heart. These conditions reduce the heart’s ability to pump enough blood around the body.

- Severe infection

- Disorders of the central nervous system such as Parkinsons disease

- Endocrine conditions, such as hypothyroidism (underactive thyroid), hyperthyroidism (overactive thyroid), Addison’s disease (adrenal insufficiency), low blood sugar, and diabetes.

- Vasovagal attack (fainting)

- Sudden change of position for example sitting/ lying to standing


Treatment for low blood pressure

The treatment for hypotension depends on its cause. Asymptomatic (no symptoms) hypotension in healthy people usually does not require treatment.

Only a small number of people who have low blood pressure are prescribed medication to treat the condition. For example, some elderly people may experience symptoms when changing posture, and are sometimes given medication to constrict (narrow) their arteries.

If you are suffering from postural hypotension there are several lifestyle changes that can be made such as :

- Drinking plenty of fluids, like water
- Drinking little or no alcohol
- Increasing salt intake
- Standing up slowly
- Gradually sitting up for longer periods of time if you’ve had to stay in bed for a long time.

Using compression stockings that apply pressure to the lower body may also help with low blood pressure. These garments drive blood from the legs to the heart and brain and help blood circulate through the body.

If your medication is suspected of causing hypotension the doctor will probably advise a change of drug or dosage.

Taking medicine to raise blood pressure, reduce signs and symptoms, and treat related conditions. Medicines include ephedrine, phenylephrine, fludrocortisone, beta blockers, and nonsteroidal anti-inflammatory medicines.

For further help and information on this subject click on Low blood pressure (hypotension) to take you to our Further information and Support Groups page