Low blood pressure, or hypotension, is a state in which the volume or force of blood pushing on the walls of the body's veins and arteries is lower than normal. Blood pressure that remains too low can interfere with the amount of blood and oxygen reaching the heart, brain and other vital organs. There are many possible causes of hypotension, ranging from medication to vitamin deficiencies to serious underlying medical problems.
Alcohol and Prescription Medication
According to the Mayo Clinic, a number of medications may cause your blood pressure to become abnormally low. These medications may include diuretics or water pills, painkillers, anti-anxiety medications, alpha and beta blockers that are commonly used to treat high blood pressure, prostate problems, glaucoma or migraines, drugs for Parkinson's disease and tricyclic antidepressants such as nortriptyline and amitriptyline. Sildenafil--a drug used to treat male erectile dysfunction--may also cause low blood pressure, particularly if used in combination with other heart medications such as nitroglycerine.
Alcohol can also lead to hypotension because it dilates blood vessels and inhibits the centers in the brain responsible for helping to regulate blood pressure, according to the Merck Manuals Online Medical Library.
Medical Conditions
Certain underlying medical conditions can cause abnormally low blood pressure. Heart disease, heart valve disorders, damage to the heart from a heart attack, extremely fast heartbeat, extremely slow heartbeat or abnormal heart rhythm can all impair the heart's ability to pump and circulate blood, thereby causing abnormal blood pressure, according to Merck.
Hormone or endocrine problems such as hypothyroidism--characterized by insufficient thyroid hormone--or hyperthyroidism (characterized by overproduction of thyroid hormone) may significantly lower blood pressure. Addison's disease--a condition caused by the adrenal gland's failure to produce enough of the hormone cortisol--may also lead to hypotension, according to the Mayo Clinic.
Pregnant women may also experience an abnormal drop in blood pressure, particularly during the first 24 weeks of pregnancy as the circulatory system expands. Blood pressure typically returns to its pre-pregnancy level after birth.
Other medical conditions that can trigger low blood pressure include diabetes and low blood sugar, Parkinson's disease, dehydration and diarrhea. If dehydration is left untreated, it can lead to a life-threatening condition known as hypovolemic shock. This causes a sudden drop in blood pressure and, possibly, death within a few hours.
Other Causes
Severe infection, or septicemia, is another possible cause of abnormally low blood pressure. When an infection enters the bloodstream, it can lead to septic shock and a potentially fatal drop in blood pressure, according to the Mayo Clinic.
Anaphylaxis--a severe, whole-body allergic reaction--can occur in response to medications, foods and many other allergens. When the immune system reacts, it causes a severe drop in blood pressure, along with hives, a swollen tongue, mouth or face and breathing problems.
Malnutrition or dietary deficiencies can also cause low blood pressure. For example, people lacking vitamin B-12 and folate may develop anemia--a condition characterized by too few red blood cells--which can interfere with the flow of oxygenated blood throughout the body. This causes low blood pressure, fatigue and weakness.
According to the National Institutes of Health, changes in body position can also cause low blood pressure. Orthostatic hypotension is a specific type of low blood pressure that occurs only when making a sudden shift in body position--usually from a sitting or kneeling to a standing position. In these cases, blood pressure usually only stays low for a few moments and then returns to normal.
