What is orthostatic hypotension?

Orthostatic hypotension refers specifically to a drop in blood pressure that occurs when a person moves from a sitting or lying position to a standing position. This condition can happen due to a variety of factors, such as dehydration, certain medications, or autonomic nervous system disorders. When someone stands up, gravity causes blood to pool in the legs, and the body typically compensates by constricting blood vessels and increasing heart rate to maintain blood flow to the brain. If this compensatory response is insufficient, it can lead to a sudden decrease in blood pressure, resulting in dizziness, lightheadedness, or even fainting.

In contrast, the other provided options do not accurately describe orthostatic hypotension. An increase in blood pressure while sitting suggests no change or an elevation rather than the typical drop associated with standing. A sudden rise in blood pressure would indicate a different issue, such as hypertensive crisis, which is contrary to the characteristics of orthostatic hypotension. Lastly, fluctuating blood pressure throughout the day might suggest normal variances in blood pressure but does not specifically define the phenomenon of blood pressure changes upon standing.