Many people do not understand how BP (blood pressure) is measured.

High blood pressure refers to a systolic and/or diatsolic number that is higher than the normal.

Blood pressure readings are measured and usually given as two numbers.

For example, 130 over 75 is written as 130/75 mmHg).
The top number is your systolic pressure, the pressure created when your heart beats. It is considered high if it is consistently over 140.
 
The bottom number is your diastolic pressure, the pressure inside blood vessels when the heart is at rest. It is considered high if it is consistently over 90.

Either or both of these numbers may be too high.

Normal blood pressure. Your blood pressure is normal if it's below 120/80 mm Hg. However, some doctors recommend 115/75 mm Hg as a better goal. Once blood pressure rises above 115/75 mm Hg, the risk of cardiovascular disease begins to increase.

After age 50. Both numbers in a blood pressure reading are important. But after age 50, the systolic reading is even more significant. Isolated systolic hypertension (ISH) — when diastolic pressure is normal but systolic pressure is high — is the most common type of high blood pressure among people older than 50.

Your are approaching a high blood pressure problem or have pre-hypertension when your systolic blood pressure is between 120 and 139 or your diastolic blood pressure is between 80 and 89. To make sure these readings are reliable several should be taken.