Causes low blood pressure

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 blood 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 getting 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 long periods of 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 Symptoms of low blood pressure (hypotension) may include:

Blurred or fading 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: