Diagnosis

A blood pressure test diagnoses elevated blood pressure. This often involves an inflatable arm cuff placed around your arm and a pressure-measuring gauge.

A blood pressure reading, given in millimeters of mercury (mm Hg), has two numbers. The first, or upper, number measures the pressure in your arteries when your heart beats (systolic pressure). The second, or lower, number measures the pressure in your arteries between beats (diastolic pressure).

According to the American Heart Association, your blood pressure is normal if it is 120/80 mm Hg or lower. Other blood pressure measurements fall into the following categories:

• Elevated blood pressure. Elevated blood pressure is a systolic pressure ranging from 120 to 129 mm Hg and a diastolic pressure below (not above) 80 mm Hg. Elevated blood pressure tends to get worse over time unless steps are taken to control blood pressure.
• Stage 1 hypertension. Stage 1 hypertension is a systolic pressure ranging from 130 to 139 mm Hg or a diastolic pressure ranging from 80 to 89 mm Hg.
• Stage 2 hypertension. Stage 2 hypertension is a systolic pressure of 140 mm Hg or higher or a diastolic pressure of 90 mm Hg or higher.

Because blood pressure tends to vary, a diagnosis of elevated blood pressure is based on the average of two or more blood pressure readings taken on separate occasions in a consistent manner. The first time, your blood pressure generally should be measured in both arms to determine if there's a difference. After that, the arm with the higher reading should be used.

Your doctor might suggest a six-hour or 24-hour blood pressure monitoring test called ambulatory blood pressure monitoring. The device used for this test measures your blood pressure at regular intervals over six or 24 hours and provides a more accurate picture of blood pressure changes over an average day and night (for the 24 hours). However, these devices aren't available in all medical centers, and insurance may not cover them.

Your doctor might also recommend that you use a home blood pressure monitor, preferably one that can store your readings in its memory, to check your blood pressure regularly. If so, he or she should show you how to use it properly.