Review Low blood pressure is generally considered to be less than 90 millimeters of mercury (mm Hg) for the top number (systolic) or 60 mm Hg for the bottom number (diastolic). What is considered low pressure for one person may be fine for another. Low blood pressure may cause no noticeable symptoms, or it may cause dizziness and fainting. Sometimes low blood pressure can be life-threatening. The causes of low blood pressure can range from dehydration to serious medical conditions. It is important to find out what causes low blood pressure so that it can be treated, if necessary. Types of low blood pressure include: Orthostatic hypotension (postural hypotension). It is a sudden drop in blood pressure when standing up from a sitting position or after lying down. Causes include dehydration, prolonged bed rest, pregnancy, certain medical conditions and certain medications. This type of low blood pressure is common in older adults. Postprandial hypotension. This drop in blood pressure occurs 1 to 2 hours after eating. It is most likely to affect older adults, especially those with high blood pressure or autonomic nervous system diseases such as Parkinson's disease. Eating small, low-carbohydrate meals, drinking more water and avoiding alcohol can help reduce symptoms. Neurally mediated hypotension. This is a drop in blood pressure that occurs after standing for a long time. This type of low blood pressure most often affects young adults and children. It can result from abnormal communication between the heart and brain. Multisystemic atrophy with orthostatic hypotension. Also called Shy-Drager syndrome, this rare disorder affects the nervous system that controls involuntary functions such as blood pressure, heart rate, breathing and digestion. It is associated with having very high blood pressure while lying down. Symptomy Low blood pressure (hypotension) symptoms may include:

• Blurred or diminishing vision
• Dizziness or photophobia
• Fainting
• Fatigue
• Concentration problems
• Nudity

For some people, low blood pressure can be a sign of an underlying disease, especially when it drops suddenly or occurs with symptoms. A sudden drop in blood pressure can be dangerous. A change of just 20 mm Hg - for example, a drop from 110 mm Hg systolic to 90 mm Hg systolic - can cause dizziness and fainting. Large drops, such as those caused by uncontrolled bleeding, severe infections or allergic reactions, can be life-threatening. Extreme low blood pressure can lead to a condition known as shock. Symptoms of shock include:

• Disorientation, especially in the elderly
• Cold, moist skin
• Decrease in skin coloration (pallor)
• Fast, shallow breathing
• Faint and rapid pulse

Drugs that can cause low blood pressure Some medications can cause low blood pressure, including:

• Aqueous pills (diuretics) such as furosemide (Lasix) and hydrochlorothiazide (Microzide)
• Alpha-blockers such as prazosin (Minipress)
• Beta-blockers such as atenolol (Tenormin) and propranolol (Inderal, Innopran XL, Hemangeol)
• Parkinson's disease medications such as pramipexole (Mirapex) or drugs containing levodopa
• Some types of antidepressants (tricyclic antidepressants), including doxepin (Silenor) and imipramine (Tofranil)
• Erectile dysfunction medications, including sildenafil (Revatio, Viagra) or tadalafil (Adcirca, Alyq, Cialis), especially if taken with the epinephrine drug nitroglycerin (Nitrostat, Nitro-Dur, Nitromist)

Conditions that can cause low blood pressure Medical conditions that can cause low blood pressure include: Pregnancy. Changes during pregnancy cause rapid expansion of blood vessels. These changes can cause a drop in blood pressure. Low blood pressure is common in the first 24 weeks of pregnancy. Blood pressure usually returns to pre-pregnancy levels after the baby is born. Diseases of the heart and heart valves. Heart attack, heart failure, heart valve disease and very low heart rhythm (bradycardia) can cause low blood pressure. Hormone-related diseases (endocrine disorders). Conditions affecting the parathyroid or adrenal glands, such as Addison's disease, can cause blood pressure to drop. Low blood sugar (hypoglycemia) and, sometimes, diabetes can also lower blood pressure. Drainage. When the body does not have enough water, the amount of blood in the body (blood volume) decreases. This can cause a drop in blood pressure. Fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise can lead to dehydration. Blood loss. Loss of large amounts of blood, such as from trauma or internal bleeding, also reduces blood volume, leading to a significant 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). Symptoms of a severe allergic reaction include a sudden and dramatic drop in blood pressure. Lack of nutrients in the diet. Low levels of vitamin B-12, folate and iron can cause the body to not produce enough red blood cells (anemia), which can lead to low blood pressure.   [cool_tag_cloud on_single_display="local"]