Orthostatic hypotension, also known as
postural hypotension,
orthostasis, and colloquially as
head rush or
dizzy spell, is a form of
low blood pressure in which a person's
blood pressure falls when suddenly standing up or stretching. In medical terms, it is defined as a fall in systolic blood pressure of at least 20 mm Hg or diastolic blood pressure of at least 10 mm Hg when a person assumes a standing position.