Hypotension or low blood pressure refers to a systolic blood pressure below 90 mm Hg, or a diastolic blood pressure below 60 mm Hg. Sometimes they occur together. It can be caused by a variety of factors, such as dehydration, cardiovascular and neurovascular problems, or medications. Hypotension can be life-threatening, especially when it is associated with shock. It can lead to a range of symptoms, such as dizziness, lightheadedness, and fainting.