Diagnosing High Blood Pressure

High blood pressure is usually diagnosed in people who have no symptoms. Blood pressure is best measured with an automated blood pressure machine: either at home (home blood pressure), in the pharmacy, or at your doctor’s office (clinic blood pressure). To diagnose high blood pressure, several high readings must be recorded at different times.

When your blood pressure is measured, two numbers are recorded. The top number is called the “systolic” pressure, and the bottom number is the “diastolic” pressure. Both numbers are important. If either the top or the bottom number is consistently above the target, then blood pressure is considered high.

High blood pressure is usually defined as a “clinic blood pressure” consistently above 140/90 mm Hg (“140 over 90”) or “home blood pressure” consistently above 135/85 mm Hg (“135 over 85”). For people with other medical issues such as diabetes or kidney disease, there may be a different cut-off.

Some people have high blood pressure at home and normal blood pressure in the clinic; other people may have the opposite. If there are inconsistencies between home and clinic blood pressures, your doctor may suggest you measure blood pressure at home more consistently, or may suggest a 24-hour hour recording of your blood pressure. If you are measuring blood pressure at home, it is important to use a validated monitor and proper technique.

Your doctor may check your blood pressure at every visit, or less frequently. It is important to see your doctor at least once per year for a check-up including blood pressure measurement. It may be reasonable to check it outside of the clinic on occasion as well (in the pharmacy, for example).