How to read your blood pressure

So you’re seeing the doctor for an annual checkup and the medical assistant wraps something around your arm. It is connected to a machine that reads your blood pressure.

What do your blood pressure numbers mean?

Your blood pressure is the force exerted by circulating blood throughout the body.

Top number (systolic)

Also known as the systolic number, this value indicates when a single heartbeat is at its maximum pressure (when your heart is pushing blood out of its chamber).

Bottom number (diastolic)

The bottom number is called the diastolic number and indicates when a single heartbeat is at a minimum pressure (when your heart is in between beats).

Measuring blood pressure

The systolic and diastolic numbers are measured in millimeters of mercury (mm HG). (The pressure required to move mercury a specific distance up a glass tube.)

Normal blood pressure

  • Systolic: below 120
  • Diastolic: below 80

Borderline high blood pressure

  • Systolic: 120-139
  • Diastolic: 80-89

High blood pressure

  • Systolic: 140 or higher
  • Diastolic: 90 or higher
Last reviewed: 
May 2018

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