All those with unusually low blood pressure, please remain seated. Indeed, for people with a condition known as orthostatic hypotension, the act of standing up can cause sudden drops in blood pressure that sometimes lead to dizziness or fainting.

Yet many individuals—especially women in their 20s and 30s—may register very low blood pressure readings all of the time without feeling any ill-effects.

"There are people who function very well with 80 to 90 millimeters of mercury of systolic blood pressure, particularly women, who can have these low blood pressure readings without any symptoms," says Vito Campese, M.D., USC professor of medicine.

Can routine blood pressure readings ever be too low? Although very low blood pressure can be an expression of bleeding, volume depletion, over-medication, or certain neurological conditions, it is not necessarily cause for alarm, according to Campese.

"We are not usually concerned about low blood pressure unless the patient is symptomatic," he says. The patients most likely to be symptomatic are those with a significant drop in blood pressure when standing.

Not so in Europe, where asymptomatic hypotension is routinely recognized and treated. In America, however, physicians are likely to wait until a patient experiences symptoms such as dizziness or fainting-the result of reduced blood flow to the brain-before advising corrective measures.

Treatment for such patients usually consists of minor lifestyle changes—a high-salt diet, exercise (particularly exercise that improves muscle tone in the lower legs), or wearing support hosiery.

"If those steps don't help, then there are a number of medications that can be used," says Campese.