Low Bood Pressure
Low blood pressure (Hypotension) might seem desirable, and for some people, it causes no problems.
However, for many people, abnormally low blood pressure (hypotension) can cause dizziness and fainting.
In severe cases, low blood pressure can be life-threatening. A blood pressure reading lower than 90 milli meters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic) is generally considered low blood pressure.
The causes of low blood pressure can range from dehydration to serious medical or surgical disorders.
It’s important to find out what’s causing your low blood pressure so that it can be treated.
Causes. Conditions that can cause low blood pressure.
Medical conditions that can cause low blood pressure include:
Pregnancy. Because the circulatory system expands rapidly during pregnancy, blood pressure is likely to drop. Pressure usually returns to your pre-pregnancy level after you’ve given birth.
Heart problems. Some heart conditions that can lead to low blood pressure include extremely low heart rate (bradycardia), heart valve problems, heart attack and heart failure.
Endocrine problems. Thyroid conditions such as parathyroid disease, adrenal insufficiency (Addison’s disease), low blood sugar (hypoglycemia) and, in some cases, diabetes can trigger low blood pressure.
Dehydration.When your body loses more water than it takes in, it can cause weakness, dizziness and fatigue. Fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise can lead to dehydration.
Blood loss. Losing a lot of blood, such as from a major injury or internal bleeding, reduces the amount of blood in your body, leading to a severe drop in blood pressure.
Severe infection (septicemia).
When an infection in the body enters the bloodstream, it can lead to a life-threatening drop in blood pressure called septic shock.
Severe allergic reaction (anaphylaxis). Common triggers of this severe and potentially life-threatening reaction include foods, certain medications, insect venoms and latex.
Anaphylaxis can cause breathing problems, itching, a swollen throat and a dangerous drop in blood pressure.
Lack of nutrients in your diet. A lack of the vitamins B-12 and folate can keep your body from producing enough red blood cells (anemia), causing low blood pressure.
Medications that can cause low blood pressure.
Some medications can cause low blood pressure, including:
Water pills (diuretics), such as furosemide (Lasix) and hydrochlorothiazide (Maxzide, Microzide, others). Alpha blockers, such as prazosin (Minipress).
Beta blockers, such as atenolol (Tenormin) and propranolol (Inderal, Inoperand XL, others).
Drugs for Parkinson’s disease, such as pramipexole (Mirapex) or those containing levodopa.
Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor) and imipramine (Tofranil).
Drugs for erectile dysfunction, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Cialis), particularly when taken with the heart medication nitroglycerin.
Types of low blood pressure
Doctors often break down low blood pressure (hypotension) into categories,
depending on the causes and other factors. Some types of low blood pressure include:
Low blood pressure on standing up (orthostatic, or postural, hypotension).
This is a sudden drop in blood pressure when you stand up from a sitting position or after lying down.
Gravity causes blood to pool in your legs when you stand. Ordinarily, your body compensates by increasing your heart rate and constricting blood vessels, thereby ensuring that enough blood returns to your brain.
But in people with orthostatic hypotension, this compensating mechanism fails and blood pressure falls, leading to dizziness, lightheadedness, blurred vision and even fainting.
Orthostatic hypotension can occur for various reasons, including dehydration,
prolonged bed rest, pregnancy, diabetes, heart problems, burns, excessive heat, large varicose veins and certain neurological disorders.
A number of medications also can cause orthostatic hypotension, particularly drugs used to treat high blood pressure —diuretics, beta blockers, calcium channel blockers and angiotensin-converting enzyme (ACE) inhibitors — as well as antidepressants and drugs used to treat Parkinson’s disease and erectile dysfunction.
Orthostatic hypotension is especially common in older adults, but it also affects young, otherwise healthy people who stand up suddenly after sitting with their legs crossed for long periods or after squatting for a time.
It’s also possible to have delayed orthostatic hypotension, with signs and symptoms developing 5 to 10 minutes after a change in posture.
This might be a milder form of the condition, or it could be an early stage of it.