|What are the causes of low blood pressure?
- Conditions that reduce the volume of blood, reduce cardiac output (the amount of blood
pumped by the heart), and medications are frequent reasons for low blood pressure.
- Dehydration is common among hypotension patients with prolonged nausea, vomiting, and
diarrhea. Other causes of dehydration include exercise, sweating, fever, and heat exhaustion,
or heat stroke.
- Moderate or severe bleeding can quickly deplete an individual's body of blood, leading to low
blood pressure or orthostatic hypotension. Bleeding can result from trauma, surgical
complications, or from gastrointestinal abnormalities such as ulcers, tumors, or diverticulosis.
- Severe inflammation of organs inside the body such as acute pancreatitis can cause low blood
pressure. In acute pancreatitis, fluid leaves the blood vessels to enter the inflamed tissues
around the pancreas as well as the abdominal cavity, concentrating blood and reducing its
- Weakened heart muscle can cause the heart to fail and reduce the amount of blood it pumps.
Other heart diseases as common causes of weakened heart muscle include heart attack,
medications that are toxic to the heart, infections of the muscle of the heart by viruses
(myocarditis), and diseases of the heart's valves such as aortic stenosis.
- Pulmonary embolism is a condition in which a blood clot in a vein (deep vein thrombosis)
breaks off and travels to the heart and eventually the lung. A large blood clot can block the
flow of blood into the left ventricle from the lungs and severely diminish the blood returning to
the heart for pumping. Pulmonary embolism is a life-threatening emergency.
- A slow heart rate (bradycardia) can decrease the amount of blood pumped by the heart.
Bradycardia (resting heart rates slower than 60 beats/minute) does not always cause low
blood pressure. In fact, some highly trained athletes can have resting heart rates in the 40s
and 50s (beats per minute) without any symptoms. (The slow heart rates are offset by more
forceful contractions of the heart that pump more blood than in non-athletes.) But in many
patients bradycardia can lead to low blood pressure, lightheadedness, dizziness, and even
- Drug toxicity: Drugs such as digoxin (Lanoxin) or beta blockers for high blood pressure, can
slow the transmission of electricity in the heart chemically and can cause bradycardia and
- An abnormally fast heart rate (tachycardia) also can cause low blood pressure. The most
common example of tachycardia causing low blood pressure is atrial fibrillation. Atrial fibrillation
is a disorder of the heart characterized by rapid and irregular electrical discharges from the
muscle of the heart causing the ventricles to contract irregularly and (usually) rapidly. Other
abnormally rapid heart rhythms such as ventricular tachycardia also can produce low blood
pressure, sometimes even life-threatening shock.
- Medications such as calcium channel blockers, beta blockers, and digoxin (Lanoxin) can slow
the rate at which the heart contracts. Some elderly people are extremely sensitive to these
medications since they are more likely to have diseased hearts and electrical conduction
- Medications used in treating high blood pressure (such as ACE inhibitors, angiotensin receptor
blockers, beta blockers, calcium channel blockers, and alpha-blockers) can excessively lower
blood pressure and result in symptomatic low blood pressure especially among the elderly.
- Water pills (diuretics) such as hydrochlorothiazide furosemide (Lasix) can decrease blood
volume by causing excessive urination.
- Medications used for treating depression, such as amitriptyline (Elavil), Parkinson's disease,
such as levodopa-carbidopa (Sinemet), erectile dysfunction (impotence), such as sildenafil
(Viagra), vardenafil (Levitra), and tadalafil (Cialis) when used in combination with nitroglycerine,
can cause low blood pressure.
- Alcohol and narcotics also can cause low blood pressure.