About one in three U.S. adults has high blood pressure. There are lots of factors that help your doctor understand your health, and your blood pressure numbers are a critical part of the picture. Charting your blood pressure shows what happens to it over time. Starting at age 20, the American Heart Association recommends a blood pressure screening at your regular healthcare visit or once every two years, if your blood pressure is less than 120/80 mm Hg.
Your blood pressure rises with each heartbeat and falls when your heart relaxes between beats. While it can change from minute to minute with changes in posture, exercise, stress or sleep, it should normally be less than 120/80 mm Hg (less than 120 systolic AND less than 80 diastolic) for an adult age 20 or over.
If your blood pressure reading is higher than normal, your doctor may take several readings over time and/or have you monitor your blood pressure at home before diagnosing you with high blood pressure.
Blood pressure is typically recorded as two numbers, written as a ratio like this:
- Systolic: The top number, which is also the higher of the two numbers, measures the pressure in the arteries when the heart beats (when the heart muscle contracts).
- Diastolic: The bottom number, which is also the lower of the two numbers, measures the pressure in the arteries between heartbeats (when the heart muscle is resting between beats and refilling with blood).
Here are the blood pressure categories defined by the American Heart Association:
- Normal: less than 120 systolic and less than 80 diastolic
- Prehypertension: 120-139 systolic or 80-89 diastolic
- High blood pressure (hypertension), stage 1: 140-159 systolic or 90-99 diastolic
- High blood pressure (hypertension), stage 2: 160 or higher systolic or 100 or higher diastolic
- Hypertensive crisis (emergency care needed): Higher than 180 systolic or higher than 110 diastolic