Orthostatic hypotension is a rapid and sudden decrease in blood pressure that occurs when a person changes position, such as rising from a sitting or lying position to standing, or when standing motionless in one position. Symptoms of orthostatic hypotension may include lightheadedness, dizziness, or fainting (syncope).

When a person sits up or stands up, the body adjusts the way it pumps blood to maintain blood flow to the brain. If the blood flow changes occur too slowly after the person stands up, the blood flow to the brain may be temporarily reduced, causing the person to feel lightheaded or to faint. Most people do not have orthostatic hypotension symptoms when they change position.

Orthostatic hypotension is often caused or made worse by dehydration. Other causes include diabetes, heart disease, and nervous system problems. Many medications cause orthostatic hypotension.

Treatment can involve adjusting medicines and increasing fluid intake.