When your doctor takes your blood pressure, it’s expressed as a measurement with two numbers, with one number on top (systolic) and one on the bottom (diastolic), like a fraction. For example, 120/80 mm Hg.
Blood pressure is a measure of the force of blood pushing against blood vessel walls. The heart pumps blood into the arteries, which carry the blood throughout the body. High blood pressure, also called hypertension, is dangerous because it makes the heart work harder to pump blood out to the body and contributes to hardening of the arteries. Most people worry about high blood pressure, which can increase your risk for heart disease or stroke, but low blood pressure can also be a problem.
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. The American Heart Association (AHA) considers blood pressure to be within the normal range when both your systolic and diastolic numbers are in these ranges.