Low Blood Pressure

Hypotension, or low blood pressure, is when your blood pressure is much lower than expected. It can happen either as a condition on its own or as a symptom of a wide range of conditions. It may not cause symptoms. But when it does, you may need medical attention.

Types of low blood pressure

Hypotension has two definitions:

• Absolute hypotension: Your resting blood pressure is below 90/60 millimeters of mercury (mm Hg).
• Orthostatic hypotension: Your blood pressure stays low for longer than three minutes after you stand up from a sitting position. (It’s normal for your blood pressure to drop briefly when you change positions, but not for that long.) The drop must be 20 mm Hg or more for your systolic (top) pressure and 10 mm Hg or more for your diastolic (bottom) pressure. Another name for this is postural hypotension because it happens with changes in posture.

Measuring blood pressure involves two numbers:

• Systolic (top number): This is the pressure on your arteries each time your heart beats.
• Diastolic (bottom number): This is how much pressure your arteries are under between heartbeats.

What is considered low blood pressure?

Low blood pressure is below 90/60 mm Hg. Normal blood pressure is above that, up to 120/80 mm Hg.

How common is low blood pressure?

Because low blood pressure is common without any symptoms, it’s impossible to know how many people it affects. However, orthostatic hypotension seems to be more and more common as you get older. An estimated 5% of people have it at age 50, while that figure climbs to more than 30% in people over 70.

Who does low blood pressure affect?

Hypotension can affect people of any age and background, depending on why it happens. However, it’s more likely to cause symptoms in people over 50 (especially orthostatic hypotension). It can also happen (with no symptoms) to people who are very physically active, which is more common in younger people.