Most doctors consider blood pressure too low only if it causes symptoms. Some experts define low blood pressure as readings lower than 90 mm Hg systolic or 60 mm Hg diastolic. If either number is below that, your pressure is lower than normal. A sudden fall in blood pressure can be dangerous.

The American Heart Association (AHA) state that although people put a lot of emphasis on the systolic number, each increase of 10 millimeters of mercury (mm Hg) in diastolic pressure among people aged 40–89 doubles their risk for heart disease or stroke.

For a normal reading, your blood pressure needs to show a top number (systolic pressure) that’s between 90 and less than 120 and a bottom number (diastolic pressure) that’s between 60 and less than 80.

A: A high diastolic blood pressure (80 mm Hg or higher) that stays high over time means you have high blood pressure, or hypertension, even when systolic blood pressure is normal. Causes of diastolic high blood pressure include both lifestyle factors and genetics, but the disease is multifactorial.

As a general guide, the ideal blood pressure for a young, healthy adult is between 90/60 and 120/80. If you have a reading of 140/90, or more, you have high blood pressure (hypertension). This puts you at greater risk of serious health conditions, such as strokes or heart attacks.

normal: less than 120/80 mm Hg. pre-hypertensive: systolic between 120-139 or diastolic between 80-89. stage 1 hypertension: systolic 140-159 or diastolic 90-99.

The first stage of hypertension is called stage 1 hypertension. The systolic pressure is 140 to 159 mm Hg or your diastolic pressure is 90 to 99 mm Hg. The next stage of hypertension, stage 2 hypertension, is diagnosed when your systolic pressure is 160 mm Hg or higher or your diastolic pressure is 100 mm Hg or higher.