Blood pressure, low

Alternative names:

hypotension; low blood pressure

Definition:

An abnormal condition in which the blood pressure is too low for normal functioning.

Considerations:

The blood pressure is normally above 90/60 mmHg (millimeters of mercury). When the blood pressure is too low there is inadequate blood flow to the heart, brain, and other vital organs.

Borderline low blood pressure for one person may be normal for another. The most important factor is how the blood pressure changes from the baseline or normal condition. A fall of 30 mmHg or more from a person's baseline is considered low blood pressure.

Common causes:

• shock
• stress or trauma
• response of blood vessels to stimulation of the vagus nerve-- called vasovagal syncope (common faint)
• sudden change in body position, usually from lying down to an upright position (orthostatic hypotension)
• allergic reaction to drugs
• anaphylaxis (a life-threatening allergic response)
• dehydration
• drugs including alcohol toxicity, anesthesia, antianxiety agents, antihypertensives, calcium channel blockers, diuretics, general anesthetics, antiarrhythmics, monoamine oxidase inhibitors, narcotic analgesics, tranquilizers, vasodilators

Note: There may be other causes of low blood pressure. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as time course, aggravating factors, relieving factors, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for low blood pressure, occurring alone or in combination with other problems.