A drop in blood pressure can cause dizziness, rapid or slow heart rate, and fainting. Lower blood pressure can happen for a variety of reasons. It may occur suddenly or over time from a chronic illness. A drop in blood pressure could be a sign of an underlying health problem. Conversely, blood pressure can become lower when health improves from making positive lifestyle changes.
Dehydration
Dehydration can be the result of sudden illness that provokes vomiting and diarrhea. When body fluids are depleted, blood pressure becomes lower. Diabetics and patients taking medications for heart disease or high blood pressure (fluid pills) can experience dehydration more easily from the compounded effect of medications and illness. Diabetics risk dehydration and hypotension (low blood pressure) if blood sugar levels become excessive, and when viruses or infection strike. Athletes who sweat excessively can become dehydrated and experience blood pressure drops.
Heart Disease
Patients with heart valve abnormalities, history of a heart attack, an enlarged heart (cardiomyopathy), or extremely rapid or slow heart rate can experience drops in blood pressure because these conditions interfere with the strength of contractions of the heart, diminishing blood flow throughout the body.
Septic Shock
Severe infections that enter the bloodstream, known as sepsis, can also produce low blood pressure, known as septic shock. The Merck Manual explains that low blood pressure from septic shock is the result of an inflammatory response. Bacteria in the bloodstream release toxic chemicals (endotoxins) that dilate the blood vessels, leading to a drop in blood pressure and decreased blood flow to the tissues and organs, according to the article "Role of Vasopressin Deficiency in the Vasodilation of Septic Shock," published in the journal Circulation in 1997.
Vasovagal Response
Fear, pain, and extreme emotions can produce a vasovagal response, leading to a drop in blood pressure from stimulation of the parasympathetic nervous system, which is responsible for slowing our blood pressure and heart rate. The term vasovagal refers to stimulation of the vagus nerve that extends from the abdomen to the brain. Fainting commonly occurs with the vasovagal response and is known as vasovagal syncope. Blood pressure that drops in response to extreme emotions is caused by dilated blood vessels in the legs and slowing of the heart rate. The same response can occur from bearing down hard, such as during toileting, hearty coughing, childbirth, or holding one's breath.
Lifestyle Changes
Weight loss and dietary changes can lower blood pressure that can be a positive change if your physician has diagnosed you with prehypertension or hypertension. Excluding salt from the diet, increased exercise, and shedding pounds can cause the blood pressure to drop. Rapid obesity reversal, following weight loss surgery, is also believed to be a cause of low blood pressure, as discussed in the article "Severe Orthostatic Hypotension Following Weight Reduction Surgery," found in the Archives of Internal Medicine, September 2001.
Postural Changes
Sudden changes in posture cause a drop in blood pressure that become more exaggerated with aging. In the absence of symptoms of dizziness, pallor, fast heart rate, sweating, or nausea, blood pressure will normalize and should pose no health problems.Older individuals should move more slowly to avoid falls from transient dizziness from sudden blood pressure drops.
Dysautonomia
Several diseases lead to autonomic nervous system dysfunction that can cause a drop in blood pressure; these include Parkinson's disease, Guillain-Barre syndrome and diabetes or alcoholism. Primary dysautonomia occurs in the absence of an underlying cause. Information from the National Institute of Neurological Disorders and Stroke (NINDS) recommends elevating the head of the bed, increased salt intake, frequent small meals, and medications that promote the reabsorption of salt from the kidneys for patients that experience drop in blood pressure from autonomic nervous system dysfunction.
