Low blood pressure: Any blood pressure that is below the normal expected for an individual in a given environment . Low blood pressure is also referred to as hypotension .

Low blood pressure is a relative term because the blood pressure normally varies greatly with activity age medications and underlying medical conditions.

Low blood pressure can result from conditions of the nervous system conditions that do not begin in the nervous system and drugs.

Neurologic conditions that can lead to low blood pressure include changing position from lying to more vertical ( postural hypotension ) stroke shock lightheadedness after urinating or defecating Parkinson's disease neuropathy and simply fright.

Nonneurologic conditions that can cause low blood pressure include bleeding infections dehydration heart disease adrenal insufficiency pregnancy prolonged bed rest poisoning toxic shock syndrome and blood transfusion reactions.

Hypotensive drugs include blood pressure drugs diuretics (water pills) heart medications (especially calcium antagonists-nifedipine/PROCARDIA beta blockers-propranolol/INDERAL and others) depression medications (such as amitriptyline / ELAVIL ) and alcohol.