Hypotension

Hypotension is abnormally low blood pressure, generally defined as a systolic reading below 90 mmHg or a diastolic reading below 60 mmHg. It may be constitutional and harmless, or it may signal an underlying problem. Common causes include dehydration, blood loss, prolonged bed rest, endocrine disorders such as adrenal insufficiency or hypothyroidism, heart conditions that reduce cardiac output, severe infection, and certain medications. Orthostatic (postural) hypotension occurs when blood pressure drops on standing because of delayed compensatory vasoconstriction.

Low blood pressure may be asymptomatic, but when blood flow to the brain becomes inadequate it can produce lightheadedness, dizziness, blurred vision, fatigue, nausea, difficulty concentrating, and fainting. These symptoms are often most pronounced on standing up.

Diagnosis rests on repeated blood pressure measurements, including readings taken while lying, sitting, and standing to detect a postural drop. Assessment also looks for the underlying cause through evaluation of hydration status, heart rhythm, and endocrine function.